Physical layer operation for multi-layer operation in a wireless system

ABSTRACT

Methods and systems are disclosed for providing physical layer resources to a plurality of medium access control (MAC) instances that are associated with different serving sites that are independently scheduled. For example, a WTRU may utilize a first physical layer configuration for transmitting to a first serving site associated with a first MAC instance. The WTRU may utilize a second physical layer configuration for transmitting to a second serving site associated with a second MAC instance. The WTRU may prevent conflicts between transmission requests from the first MAC instance and transmission requests from the second MAC instance. For example, preventing the conflicts may include utilizing one or more of time segregation or frequency segregation for transmissions associated with the first MAC instance and transmissions associated with the second MAC instance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/974,911, filed Aug. 23, 2013, which claims the benefit of U.S.Provisional Patent Application No. 61/692,548, filed Aug. 23, 2012; U.S.Provisional Patent Application No. 61/726,262, filed Nov. 14, 2012; U.S.Provisional Patent Application No. 61/808,013, filed Apr. 3, 2013; andU.S. Provisional Patent Application No. 61/821,154, filed May 8, 2013,the contents of which are hereby incorporated by reference in theirentirety.

BACKGROUND

Long Term Evolution (LTE) R11 and earlier may support multi-pointconnections with Remote Radio Heads (RRH) based architectures. However,such systems utilized a centralized scheduler on the same or differentuplink (UL) and/or downlink (DL) frequencies. Since the scheduling ofthe different transmissions were scheduled in a coordinated fashion,conflicts between scheduling orders received from differenttransmission/reception points were generally not of great concern.

The operation of a wireless transmit/receive unit (WTRU) in a network inwhich the scheduling functionality for the downlink and/or the uplinktransmissions is distributed in more than one physical location and/ornode may present some challenges. For example, some characteristics of asignal to be transmitted by a WTRU may depend on scheduling decisionsthat are made independently in each node. Without tight coordinationamong nodes (e.g., which may be unavailable if the backhaul link betweenthe nodes is associated with a relatively high latency) certain signalsmay not be properly transmitted at the WTRU side, and signals receivedat the network side may not be properly decoded.

SUMMARY

Methods and systems are described for physical layer operation when aWTRU is configured to transmit to a plurality of serving sites. Forexample, methods and systems are disclosed for providing physical layerresources to a plurality of medium access control (MAC) instances thatare associated with different serving sites that are independentlyscheduled. For example, a WTRU may utilize a first physical layerconfiguration for transmitting to a first serving site associated with afirst MAC instance. The WTRU may utilize a second physical layerconfiguration for transmitting to a second serving site associated witha second MAC instance. The WTRU may prevent conflicts betweentransmission requests from the first MAC instance and transmissionrequests from the second MAC instance (e.g., coordinate transmissionrequests). For example, preventing the conflicts may include utilizingone or more of time segregation or frequency segregation fortransmissions associated with the first MAC instance and transmissionsassociated with the second MAC instance.

For example, time segregation may be utilized for preventing conflictsbetween the uplink transmissions of the plurality of MAC instances. Whentime segregation is utilized each of the first MAC instance and thesecond MAC instance may be assigned a respective subset of subframes fortransmitting in the uplink. For example, a first subset of subframes maybe assigned to the first MAC instance and a second set of subframes maybe assigned to the second MAC instance. The subframe subsets may becompletely separated or may partially overlap. The first MAC instanceand the second MAC instance may utilize non-synchronous subframe timing.The WTRU may determine to drop at least one symbol to be transmitted tothe first serving site based on an allocated subframe of the secondserving site overlapping with an allocated subframe of the first servingsite. The symbol may be dropped in order to allow the WTRU to switch itsphysical layer configuration in order to transmit to a different servingsite. The at least one symbol that is dropped may be the last symbol inthe allocated subframe of the first serving site. In an example, the WRUmay drop the first symbol of the allocated subframe of the secondserving site.

Due to limited number of subframes available for uplink transmission,one or more uplink procedures may be modified in order to ensure uplinkresources are available for transmission to a given MAC instance. Forexample, a first hybrid automatic repeat request (HARQ) feedback timingrelationship may be applied for transmissions sent using the first MACinstance, and a second HARQ timing relationship may be applied fortransmission sent using the second MAC instance.

In an example, frequency segregation may be utilized. For example, theWTRU may transmit using a first carrier when sending transmissionassociated with the first MAC instance, and the WTRU may transmit usinga second carrier when sending transmission associated with the secondMAC instance. The carriers may be separated in the frequency domain. TheWTRU may be configured with a maximum transmit power for each MACinstance. The WTRU may be configured with a maximum transmit power fortransmitting to one or more of the first serving site or the secondserving site (e.g., a total amount of power available at any given timeinstant). The WTRU may determine that transmitting according to a firstreceived uplink grant for the first serving site and transmittingaccording to a second uplink grant for the second serving site wouldresult in the WTRU exceeding the maximum transmit power.

The WTRU may determine to scale one or more of a transmission to thefirst serving site or a transmission to the second serving site based ondetermining that transmitting according to the first received uplinkgrant for the first serving site and transmitting according to thesecond uplink grant for the second serving site would result in the WTRUexceeding the maximum transmit power. For example, scaling one or moreof a transmission to the first serving site or a transmission to thesecond serving site may include allocating power first to a physicaluplink control channel (PUCCH) transmission, and allocating remainingpower up to the maximum transmit power to one or more physical uplinkshared channel (PUSCH) transmissions. The WTRU may include an indicationthat a transmission has been scaled due to power constraints in one ormore of the transmission to the first serving site or the transmissionto the second serving site. The WTRU may determine which transmission toscale based on a priority of data to be transmitted to the first servingsite and a priority of data to be transmitted to the second servingsite.

The WTRU may transmit a quality of service (QoS) status report (QSR) toone or more of the first serving site or the second serving site. TheQSR may be sent based on determining that a QoS requirement for at leastone radio bearer is not being met. The QSR may include informationrelated to bearers associated with different serving sites and/orbearers mapped to a plurality of serving sites. The WTRU may determine arelative priority between a first uplink grant associated with the firstMAC instance and a second uplink grant associated with the second MACinstance based on explicit indications regarding priority received froma network entity. The priority may be used to prioritize a transmissionto one of the serving sites in case of conflict.

The WTRU may report power headroom information for each of transmissionsassociated with the MAC instance and transmissions associated with thesecond MAC instance to the first serving site. For example, the powerheadroom information for each of transmissions associated with the MACinstance and transmissions associated with the second MAC instance tothe first serving site may be reported based on determining to scale atleast one transmission to one or more of the first serving site or thesecond serving site.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIG. 1D is a system diagram of an another example radio access networkand another example core network that may be used within thecommunications system illustrated in FIG. 1A;

FIG. 1E is a system diagram of an another example radio access networkand another example core network that may be used within thecommunications system illustrated in FIG. 1A; and

FIG. 2 is a block diagram conceptually illustrating priority rules thatmay be used to resolve contention between MAC instances.

DETAILED DESCRIPTION

A detailed description of illustrative examples will now be describedwith reference to the various Figures. Although this descriptionprovides a detailed example of possible implementations, it should benoted that the details are intended to be exemplary and in no way limitthe scope of the application.

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, and/or 102 d (whichgenerally or collectively may be referred to as WTRU 102), a radioaccess network (RAN) 103/104/105, a core network 106/107/109, a publicswitched telephone network (PSTN) 108, the Internet 110, and othernetworks 112, though it will be appreciated that the disclosedembodiments contemplate any number of WTRUs, base stations, networks,and/or network elements. Each of the WTRUs 102 a, 102 b, 102 c, 102 dmay be any type of device configured to operate and/or communicate in awireless environment. By way of example, the WTRUs 102 a, 102 b, 102 c,102 d may be configured to transmit and/or receive wireless signals andmay include user equipment (UE), a mobile station, a fixed or mobilesubscriber unit, a pager, a cellular telephone, a personal digitalassistant (PDA), a smartphone, a laptop, a netbook, a personal computer,a wireless sensor, consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106/107/109, theInternet 110, and/or the networks 112. By way of example, the basestations 114 a, 114 b may be a base transceiver station (BTS), a Node-B,an eNode B, a Home Node B, a Home eNode B, a site controller, an accesspoint (AP), a wireless router, and the like. While the base stations 114a, 114 b are each depicted as a single element, it will be appreciatedthat the base stations 114 a, 114 b may include any number ofinterconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 103/104/105, which mayalso include other base stations and/or network elements (not shown),such as a base station controller (BSC), a radio network controller(RNC), relay nodes, etc. The base station 114 a and/or the base station114 b may be configured to transmit and/or receive wireless signalswithin a particular geographic region, which may be referred to as acell (not shown). The cell may further be divided into cell sectors. Forexample, the cell associated with the base station 114 a may be dividedinto three sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 115/116/117,which may be any suitable wireless communication link (e.g., radiofrequency (RF), microwave, infrared (IR), ultraviolet (UV), visiblelight, etc.). The air interface 115/116/117 may be established using anysuitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 103/104/105 and the WTRUs 102a, 102 b, 102 c may implement a radio technology such as UniversalMobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA),which may establish the air interface 115/116/117 using wideband CDMA(WCDMA). WCDMA may include communication protocols such as High-SpeedPacket Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may includeHigh-Speed Downlink Packet Access (HSDPA) and/or High-Speed UplinkPacket Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface115/116/117 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106/107/109.

The RAN 103/104/105 may be in communication with the core network106/107/109, which may be any type of network configured to providevoice, data, applications, and/or voice over internet protocol (VoIP)services to one or more of the WTRUs 102 a, 102 b, 102 c, 102 d. Forexample, the core network 106/107/109 may provide call control, billingservices, mobile location-based services, pre-paid calling, Internetconnectivity, video distribution, etc., and/or perform high-levelsecurity functions, such as user authentication. Although not shown inFIG. 1A, it will be appreciated that the RAN 103/104/105 and/or the corenetwork 106/107/109 may be in direct or indirect communication withother RANs that employ the same RAT as the RAN 103/104/105 or adifferent RAT. For example, in addition to being connected to the RAN103/104/105, which may be utilizing an E-UTRA radio technology, the corenetwork 106/107/109 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106/107/109 may also serve as a gateway for the WTRUs102 a, 102 b, 102 c, 102 d to access the PSTN 108, the Internet 110,and/or other networks 112. The PSTN 108 may include circuit-switchedtelephone networks that provide plain old telephone service (POTS). TheInternet 110 may include a global system of interconnected computernetworks and devices that use common communication protocols, such asthe transmission control protocol (TCP), user datagram protocol (UDP)and the internet protocol (IP) in the TCP/IP internet protocol suite.The networks 112 may include wired or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another core network connected to one or moreRANs, which may employ the same RAT as the RAN 103/104/105 or adifferent RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment. Also, embodiments contemplate that thebase stations 114 a and 114 b, and/or the nodes that base stations 114 aand 114 b may represent, such as but not limited to transceiver station(BTS), a Node-B, a site controller, an access point (AP), a home node-B,an evolved home node-B (eNodeB), a home evolved node-B (HeNB), a homeevolved node-B gateway, and proxy nodes, among others, may include someor all of the elements depicted in FIG. 1B and described herein.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 115/116/117. For example, in one embodiment,the transmit/receive element 122 may be an antenna configured totransmit and/or receive RF signals. In another embodiment, thetransmit/receive element 122 may be an emitter/detector configured totransmit and/or receive IR, UV, or visible light signals, for example.In yet another embodiment, the transmit/receive element 122 may beconfigured to transmit and receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 115/116/117.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that may not be physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 115/116/117from a base station (e.g., base stations 114 a, 114 b) and/or determineits location based on the timing of the signals being received from twoor more nearby base stations. It will be appreciated that the WTRU 102may acquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 103 and the core network 106according to an embodiment. As noted above, the RAN 103 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 115. The RAN 103 may also be in communicationwith the core network 106. As shown in FIG. 1C, the RAN 103 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 115. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 103. TheRAN 103 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 103 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 103 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 103 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1D is a system diagram of the RAN 104 and the core network 107according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 107.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1D, theeNode-Bs 160 a, 160 b, 160 c may communicate with one another over an X2interface.

The core network 107 shown in FIG. 1D may include a mobility managementgateway (MME) 162, a serving gateway 164, and a packet data network(PDN) gateway 166. While each of the foregoing elements are depicted aspart of the core network 107, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 162 may be connected to each of the eNode-Bs 160 a, 160 b, 160 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 164 may be connected to each of the eNode-Bs 160 a,160 b, 160 c in the RAN 104 via the S1 interface. The serving gateway164 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 164 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 164 may also be connected to the PDN gateway 166,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 107 may facilitate communications with other networks.For example, the core network 107 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 107 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 107 and the PSTN 108. In addition, the corenetwork 107 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1E is a system diagram of the RAN 105 and the core network 109according to an embodiment. The RAN 105 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, 102 c over the air interface 117. As will be furtherdiscussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 105, andthe core network 109 may be defined as reference points.

As shown in FIG. 1E, the RAN 105 may include base stations 180 a, 180 b,180 c, and an ASN gateway 182, though it will be appreciated that theRAN 105 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 180 a, 180 b,180 c may each be associated with a particular cell (not shown) in theRAN 105 and may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 117. In oneembodiment, the base stations 180 a, 180 b, 180 c may implement MIMOtechnology. Thus, the base station 180 a, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a. The base stations 180 a, 180 b, 180 c may alsoprovide mobility management functions, such as handoff triggering,tunnel establishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 182 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 109, and the like.

The air interface 117 between the WTRUs 102 a, 102 b, 102 c and the RAN105 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, 102 cmay establish a logical interface (not shown) with the core network 109.The logical interface between the WTRUs 102 a, 102 b, 102 c and the corenetwork 109 may be defined as an R2 reference point, which may be usedfor authentication, authorization, IP host configuration management,and/or mobility management.

The communication link between each of the base stations 180 a, 180 b,180 c may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 180 a, 180 b,180 c and the ASN gateway 182 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 102 c.

As shown in FIG. 1E, the RAN 105 may be connected to the core network109. The communication link between the RAN 105 and the core network 109may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 109 may include a mobile IP home agent(MIP-HA) 184, an authentication, authorization, accounting (AAA) server186, and a gateway 188. While each of the foregoing elements aredepicted as part of the core network 109, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 184 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 186 may be responsible for userauthentication and for supporting user services. The gateway 188 mayfacilitate interworking with other networks. For example, the gateway188 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 188 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1E, it will be appreciated that the RAN 105may be connected to other ASNs and the core network 109 may be connectedto other core networks. The communication link between the RAN 105 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 105 and the other ASNs. The communication link betweenthe core network 109 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

The operation of a wireless transmit/receive unit (WTRU) in a network inwhich the scheduling functionality for the downlink and/or the uplinktransmissions is distributed in more than one physical location or nodemay present some challenges. For example, a first scheduler associatedwith a first transmission layer may be included at a first MAC instanceassociated with and/or included in a first serving site (e.g., a firstRAN node such as an eNB and/or macro eNB (MeNB)). A second schedulerassociated with a second transmission layer may be included at a secondMAC instance associated with and/or included in a second serving site(e.g., a second RAN node such as an eNB and/or small cell eNB (SCeNB)).One or more signal characteristics of a transmission to and/or from aWTRU may depend on scheduling decisions that are made independently ineach node. Additionally, the scheduling nodes may communicate via arelatively high latency interface, making coordination of schedulingdecisions difficult to implement in practice.

For example, the WTRU may receive grants (e.g., dynamic grants via aPhysical Downlink Control Channel (PDCCH), semi-persistent scheduling(SPS) grants, other uplink grants, etc.) from each of the two schedulingsites. The grants may direct the WTRU to transmit over on an uplink (UL)channel (e.g., Physical Uplink Control Channel (PUCCH), Physical UplinkShared Channel (PUSCH)), and two or more grants may allocate resourcesto the WTRU that overlap in the frequency and/or time domain(s). In sucha situation, the WTRU may be unable to comply with the grant transmittedfrom one or more of the sites.

As another example, the WTRU may receive UL grants from two (or more)sites, and each received grant may be associated with a different ULchannel and/or different UL frequency bands. However, if the WTRUtransmits in accordance with each of the signaled grants, thecombination may result in the WTRU exceeding its maximum transmissionpower. In this situation, the WTRU may be unable to transmit each signalat the power level requested the receptive schedulers, increasingly thelikelihood of a failed transmission.

In an example, the WTRU may be configured to transmit uplink controlinformation (UCI) in a given subframe based on a Physical DownlinkShared Channel (PDSCH) transmission received from a first serving site.Additionally, in the same subframe the WTRU may be configured totransmit a PUSCH transmission based on a received UL grant from a secondserving site. The UCI transmission to the first site (e.g., sent via thePUCCH, PUSCH, etc.) may conflict with the PUSCH transmission to thesecond site. Such a situation may cause numerous complications. Forexample, the WTRU may attempt to include the UCI (e.g., which wasrequest by and/or pertains to transmissions associated with the firstserving site) in the PUSCH transmission sent to the second serving site;however, the second serving site may be unaware that the WTRU isincluding the UCI in the PUSCH transmission, so the second serving sitemay fail to properly decode one or more of the UCI and/or the entirePUSCH transmission.

In order to avoid and/or address such scheduling difficulties, the WTRUmay attempt to decouple transmissions and/or receptions associated withscheduling decisions made in different nodes of a network. For example,the characteristics of a signal that is to be transmitted and/orreceived from a given serving site in the network may be determinedbased on signaling originating from a single serving node of thenetwork, for example rather than signaling originating from multiplenodes of the network.

Although the examples described herein may be described with respect tooperation utilizing a first data path (e.g., may also be referred to asa first layer, a primary data path, a primary layer, etc.) that isassociated with a MeNB and a second data path (e.g., may also bereferred to as a second layer, a secondary data path, a secondary layer,etc.), the methods and systems described herein may be equallyapplicable to other network transmission/reception points that areindependently scheduled (e.g., two or more independently scheduled eNBs,two or more independently scheduled NBs, two or more independentlyscheduled RAN access nodes, etc.). The systems and methods describedherein may be applicable to one or more multi-scheduler frameworkswherein different network nodes serve as transmission/reception pointsfor different data paths

A data path may be defined based on the identity of one or more serviceaccess points (SAPs) that are used to transmit data associated with thedata path, based on the identity of one or more network interfaces ornodes that are used to transmit the data associated with the data path,based on one or more radio interfaces (e.g., X2, X2bis, X2′, Uu, etc.)that are used to transmit data associated with the data path, and/or thelike. Further, a data path may be defined based on the communicationprotocol stack (e.g., including one or more of a packet data convergenceprotocol (PDCP) layer, a radio link control (RLC) layer, a medium accesscontrol (MAC) layer, a physical (PHY) layer, etc.) that may be used todefine a processing sequence for transferring information associatedwith the data path. The information or data transmitted over a data pathmay include one or more of control plane data (e.g., non-access stratum(NAS) signaling, RRC signaling, etc.) and/or user plane data (e.g., IPpackets, etc.). Data paths may be independently scheduled from otherdata paths.

For example, in LTE Release 11, data transfer may be performed over asingle data path between the WTRU and the network. For the controlplane, there may be a direct mapping between an SRB and a LogicalChannel (LCH) over a single Uu interface (e.g., an interface between theWTRU and an eNB). For the user plane, there may be a direct mappingbetween an EPS bearer, a Data Radio Bearer (DRB), and a Logical Channel(LCH) over that same Uu interface.

However, in the presence of multiple independent schedulers, the WTRUmay be configured to utilize more than one data path, for example whereeach data path may be established between the WTRU and network nodesusing different Uu interfaces. A data path may also be referred to as alayer. For example, the WTRU may be configured to transmit and/orreceive data over multiple layers, where each layer is associated with adifferent data path. Each layer may be scheduled independently of otherlayers. Each layer may be associated with a different air interface forthe WTRU. Each layer may be associated with a serving site that servesas a transmission and/or reception point for the data path within thenetwork.

In order to support transmissions over multiple layers, a plurality ofMAC instances may be established at the WTRU. For example, the WTRU maybe configured with multiple MAC instances that are each associated witha corresponding set of physical layer parameters and/or withlayer-specific radio bearers. As an example, the WTRU may be configuredwith a set of primary layer information (e.g., which may be associatedwith a macro layer/MeNB/macro serving site) and one or more sets ofsecondary layer information (e.g., which may be associated with a smallcell layer/SCeNB/small cell serving site). A WTRU may be configured withone or more serving cells for each layer. For example, the WTRU mayperform carrier aggregation in each of the layers such thattransmissions and/or reception may occur from multiple cells within agiven layer.

For example, the WTRU may be configured to operate with one or moreserving sites (e.g., also referred to as serving eNBs) in the downlinkand/or the uplink. Each serving site may be associated with one or moreserving cells. For example, a WTRU may operate using a single servingcell (e.g., component carrier) at first serving site (e.g., a MeNB) andmay operate using a plurality of serving cells (e.g., a plurality ofcomponent carriers) at a second serving site (e.g., a SCeNB). Thus, aserving site may be associated with a plurality of serving cells. Eachserving cell of a given serving site may be configured for operation ata corresponding component carrier (CC). A serving site may support oneor multiple CCs. Each CC within a serving site may operate using adifferent frequency range than other CCs of the serving site, so thateach of the serving cells associated with a given serving site may betransmitted using a different CC. However, serving cells from differentserving sites may be transmitted using the same CC. Therefore, servingcells may be associated with the same CC but with different servingsites. A WTRU may be configured with a maximum number of serving sitesover which the WTRU may operate (e.g., 1, 2, 3, 4, etc.). An indicationof the maximum number of serving sites that the WTRU may be allowed toutilize may be signaled by the WTRU to the network as part of WTRUcapability information and/or may be determined by the network based onthe operating class of a WTRU.

A serving site may be associated with one or more Transport Channels.For example, in the uplink the WTRU may be configured to deliver data tothe physical layer using a transport channel (e.g., UL-SCH) that isassociated with a serving cell associated with a specific serving site.In an example, each transport channel may be specific to a given servingsite/layer, although the transport channel may be associated withmultiple serving cells and/or component carriers within that servingsite. For example, a UL-SCH may be associated with a specific servingsite (e.g., a serving site associated with the data path including theMeNB) and one or more component carriers associated with that servingsite (e.g., multiple component carriers that are associated with theMeNB). A transport block to be delivered to that serving site may beserved with data associated with the transport channel mapped to thatserving site. In the downlink the WTRU may be configured to receive datato at the physical layer and deliver the data to a transport channel(e.g., DL-SCH) that is associated with a serving cell associated with aspecific serving site. For example, a DL-SCH may be associated with aspecific serving site (e.g., a serving site associated with the datapath including the SCeNB) and one or more component carriers associatedwith that serving site (e.g., multiple component carriers that areassociated with the SCeNB). A transport block received at the physicallayer may be mapped to a transport channel associated with that servingsite from which the transport block was received. A given serving sitemay be associated with zero, one, or more than one UL-SCHs and zero,one, or more than one DL-SCHs.

Each serving site may be associated with a corresponding MAC instance atthe WTRU. The WTRU may be configured with multiple MAC instances. EachMAC instance may be associated with a specific serving site. The termsserving site, layer, data path, MAC instance, etc. may be usedinterchangeably herein. Each MAC instance may be associated with one ormore configured serving cells and support one or more CCs. Each UL-SCHand/or DL-SCH may be associated with a given MAC instance (e.g., aone-to-one instance between a transport channel and a MAC instance).

A MAC instance may be configured with a Primary Cell (PCell). For eachserving site (and/or MAC instance), one of its associated serving cellsmay support at least a subset of the functionality supported by aprimary serving cell (PcCell) in legacy (e.g., single-site) systems. Forexample, one or more of the serving cells of a given MAC instance maysupport PUCCH transmissions that may be utilized for sending schedulingrequests, HARQ feedback, CSI feedback, and/or the like related to theUL-SCH and/or the DL-SCH mapped to the corresponding serving site. Aserving cell that is configured to receive uplink control information(UCI) associated with the transport channels of the serving site may bereferred to as a “site PCell” and/or a “MAC primary cell.” Each MACinstance may be configured with one PCell and zero or more SCells.Further, the PCell of a primary MAC instance (e.g., the MAC instanceassociated with a MeNB) may have additional functionality specific tothat MAC instance. A serving site may be associated with a data path. Aserving site may correspond to a single data path.

In an example, physical channels of a given MAC instance may beassociated with a specific serving site. For example, a given uplinkand/or downlink physical channel may be used for transmission betweenthe WTRU and a single serving site. Similarly, a given reference signaltransmitted in the uplink and/or the downlink may be associated with thechannel between the WTRU and a single serving site. The set of physicalchannels and/or set of reference signals used for communication with acertain serving site may be mapped to one MAC instance at the WTRU.

When the WTRU is configured to operate with more than one serving site,multiple MAC instances may be utilized. For example, the WTRU mayutilize instantiate a MAC instance for each serving site it is connectedto. Each MAC instance may utilize a corresponding set of physicalchannels in order to communicate with the serving site. For example, afirst MAC in the WTRU instance may be may be configured to connect toand/or communicate with a first serving site (e.g., a MeNB), and asecond MAC instance in the WTRU may be may be configured to connect toand/or communicate with a second serving site (e.g., a SCeNB). The firstMAC instance may be associated with a first set of physical channels(e.g., a PDCCH, a PDSCH, a PUCCH, a PUSCH, etc.) that may be used fortransmissions between the WTRU and the first serving site, and thesecond MAC instance may be associated with a second set of physicalchannels (e.g., a PDCCH, a PDSCH, a PUCCH, a PUSCH, etc.) that may beused for transmissions between the WTRU and the second serving site. Thefirst MAC instance may be configured to map transport channels to itscorresponding set of physical channels.

If carrier aggregation is configured, a serving site and/or itscorresponding MAC instance may be configured for use with more than oneserving cell. For example, one of the serving cells associated with agiven serving site may be identified as a primary serving cell (e.g., aPCell). Zero or more serving cells associated with a given serving sitemay be identified as a secondary serving cell (e.g., SCell). The PCelland zero or more SCells associated with a given layer and/or servingsite may be scheduled by a single scheduler. The PCell and zero or moreSCells associated with a given layer and/or serving site may bescheduled by more than one scheduler, for example if the multipleschedulers may coordinate that scheduling so as to avoid schedulingconflicts (e.g., using a relatively low latency interface).

One or more physical channels and/or signals (e.g., reference signals)may be associated with each MAC instance. For example, a PUCCH may beassociated with a given MAC instance. The PUCCH may be configured totransport uplink control information (e.g., HARQ feedback, channel stateinformation (CSI) such as channel quality indicator (CQI), precodingmatrix indicator (PMI), rank indicator (RI), Scheduling Request (SR),etc.) associated with the corresponding MAC instance to the applicableserving site. If multiple MAC instances are configured, multiple PUCCHsmay be configured (e.g., one PUCCH for each MAC instance). If carrieraggregation is performed for a given serving site, the PUCCH may betransmitted on the primary serving cell of the MAC instance (e.g., thePCell for the MAC instance/serving site), but not on the secondaryserving cell(s) of the MAC instance (e.g., the SCell(s) for the MACinstance/serving site).

A physical broadcast channel (PBCH) may be associated with a given MACinstance. For example, the PBCH for a given MAC instance/serving sitemay transport system information associated with the corresponding MACinstance. If carrier aggregation is performed for a given serving site,the PBCH may be transmitted on the primary serving cell of the MACinstance (e.g., the PCell for the MAC instance/serving site), but not onthe secondary serving cell(s) of the MAC instance (e.g., the SCell(s)for the MAC instance/serving site).

A PUSCH may be associated with each serving cell of a given MACinstance. For example, if a given MAC instance is associated with asingle PCell and two SCell, the MAC instance may be associated withthree PUSCHs (e.g., a first PUSCH sent to the PCell, a second PUSCH sentto the first SCell, and a third PUSCH sent to the second SCell). A PUSCHmay be configured to transport information from a given transportchannel (e.g., one or more transport blocks) associated with the MACinstance. The PUSCH may be used to transmit user data and/or UCIassociated with its corresponding MAC instance.

A PDCCH and/or enhanced PDCCH (E-PDCCH) may be associated with eachserving cell of a given MAC instance. For example, for a given servingcell of a MAC instance, the WTRU may attempt to receive the PDCCH and/orE-PDCCH in at least one search space (e.g., a common search space, aWTRU-specific, etc.). If carrier aggregation is used and the carrierindication field (CIF) is configured for a given MAC instance, then theWTRU may attempt to receive the PDCCH and/or E-PDCCH in PCell of the MACinstance, but not on the zero or more SCells associated with the MACinstance. More than one E-PDCCH set may be configured for a givenserving cell associated with a MAC instance. A PDCCH and/or E-PDCCH maybe used to transport control information to the corresponding MACinstance in the WTRU. For example, one or more of PDSCH assignments,PUSCH grants, physical random access channel (PRACH) orders, transmitpower control (TPC) commands, CSI requests, aperiodic sounding referencesignal (SRS) request, and/or the like may be transmitted on the PDCCHand/or E-PDCCH. The downlink control information (DCI) received on agiven PDCCH (and/or E-PDCCH) may be applicable to the MAC instanceassociated with that PDCCH (and/or E-PDCCH).

A PRACH may be associated a serving cell of a corresponding given MACinstance. For example, each serving cell of associated with given MACinstance may be include a PRACH. The PRACH may be used for supportingcontention-based and/or non-contention-based random access (RACH)procedures for the associated MAC instance.

In an example, rather than physical channels being associated with asingle serving site, a set of one or more physical channel may beassociated with more than one serving site. For example, a given uplinktransmission by the WTRU sent over an uplink physical channel may bereceived by multiple serving sites (e.g., eNBs), for example using a MACinstance that is common to multiple serving sites. Thus, an uplinkphysical channel (e.g., and/or reference signal) may be used fortransmission of data and/or control information associated with morethan one serving site, and a downlink physical channel (e.g., and/orreference signal) may be used for reception of data and/or controlinformation associated with more than one serving site. The set ofphysical channels and/or reference signals used for communication withmultiple serving sites may be mapped to a single MAC instance that isassociated with each of the serving sites. A MAC instance that isassociated with transmission to/from multiple serving sites may bereferred to as a common MAC instance.

In the uplink, one or more characteristics of a transmission for aphysical channel associated with a common MAC instance may be determinedsemi-statically. For example, the WTRU may determine one or moreparameters to apply for an uplink transmission (e.g., PUSCH, PUCCH,etc.) without relying on and/or receiving dynamic control signaling froma serving site. For example, in some instances one or more of a resourceblock assignment, a modulation and coding scheme (MCS), a demodulationreference signal (DM-RS) characteristic, transmission of aperiodic CSI,a HARQ characteristic, an SRS transmission and/or the like may bepre-determined or configured semi-statically, rather dynamicallyindicated or scheduled. Parameters such as the transmission power and/ortiming advance used for semi-statically configured transmissions (e.g.,transmission that are not dynamically scheduled) may be determined basedon one or more measurements taken with respect to one or more of theserving sites. For example, measurements may be performed in order todetermine one or more of a timing reference, a pathloss reference, etc.for one or more of the serving sites, and timing adjustmentmessages/commands and/or power adjustment messages/commands may bereceived from one or more of the serving sites.

One or more physical channels and/or reference signals may be associatedwith a common MAC instance. For example, a single PUCCH may be utilizedfor transporting uplink control information (e.g., CSI, SchedulingRequest, etc.) that may be applicable to various serving sites. ThePUCCH may be associated with a common MAC instance, and the common MACinstance may be associated with a plurality of serving sites.

In an example, each serving cell associated with a common MAC instance(e.g., one or more serving cells for each of multiple serving sites) mayhave an associated PUSCH. The PUSCHs may be associated with the commonMAC instance and may be used to for transmitting one or more transportblock(s) including information to be processed at one or more of theserving sites. For example, the WTRU may include an indication of whichserving site (e.g., and/or which cell of a serving site) is the intendeddestination of the data included in the transport block. The indicationmay be included in-band within a transport block and/or may be includedas additional control information in the PUSCH transmission. Forexample, the indication of which serving site the PUSCH is associatedwith may include a serving site indicator and/or a logical channelidentifier. A logical channel identifier may be used if the logicalchannel identifiers are unique across the different serving sites.

In an example, a single transport block may include data to be deliveredto more than one serving site. For example, a transport block may betransmitted by the WTRU and received at a given serving site. A servingsite (e.g., eNB) that successfully decodes the transport block mayforward the transport block (and/or one or more portions of thetransport block relevant to another serving site) to another servingsite that is the destination of some or all of the data included in thetransport block. Such a scheme may be used to achieve macrodiversity.Additionally, one or more serving cells associated with a common MACinstance may include a PRACH, for example in order to supportcontention-based and/or non-contention-based random access procedures.

When multiple instances of a given type of physical channel exist (e.g.,an instance of a given physical channel for each MAC instance), one ormore transmission properties associated with a given instance of a typeof physical channel may be configured individually. For example, one ormore transmission properties associated with a given instance of a typeof physical channel may be configured separately for each MAC instance.As an example, a first transmission power may be associated with a PUCCHassociated with a first MAC instance and a second transmission powerlevel may be associated with a PUCCH associated with a second MACinstance. In an example, transmission power and/or the identity of areference signal(s) used for a path loss reference determination may beconfigured, maintained, and/or updated independently for each MACinstance. Transmission timing and/or the identity of a referencesignal(s) used for deriving transmission timing may be configured,maintained, and/or updated independently for each MAC instance.

If timing and/or power adjustments are performed independently for eachMAC instance, the uncoordinated nature of the adjustments may leadsituations where concurrent operation of two physical channelsassociated with different MAC instances may become infeasible due tolarge disparities between transmission properties associated with eachof the MAC instances. For example, transmission timing differencesbetween the different MAC instances that exceed the duration of a cyclicprefix may infeasible in some modes of operation. When the differencebetween transmission timing associated with two or more MAC instances(and/or transmission power associated with two or more MAC instances)exceeds a predetermined and/or configured threshold, the WTRU may takeone or more corrective actions in using one or more of the MACinstances. For example, upon determining that the timing and/or powerdifferences between MAC instances exceed a threshold, the WTRU maydetermine to declare radio link failure (RLF) for one or more of the MACinstances. For example, the WTRU may stop transmissions for the physicalchannel(s) associated with one or more of the MAC instances. The WTRUmay trigger transmission of an RRC message, such as a measurementreport, based on determining the difference between transmission timingassociated with two or more MAC instances (and/or transmission powerassociated with two or more MAC instances) exceeds the threshold. In anexample, the WTRU may perform one or more actions that are performedupon receiving a configuration (and/or reconfiguration) that it isunable to comply with upon determining that the timing and/or powerdifferences between MAC instances exceeds a threshold. In an example,the WTRU may prioritize a transmission for one of the MAC instances(e.g., according to prioritization rules as described herein) upondetermining that the timing and/or power differences between MACinstances exceed a threshold. The WTRU may drop or truncate in time(e.g., skip one or more symbols) a transmission for a MAC instance upondetermining that the timing and/or power differences between MACinstances exceed a threshold.

When a timing and/or power difference between MAC instances exceeds thethreshold, the WTRU may use various criteria for determining which ofthe MAC instances should be used to take corrective action (e.g.,declare RLF, stop transmissions, dropping transmissions or symbols,etc.). For example, the MAC instance to use for taking corrective actionmay be selected based on whether the MAC instance is associated withtransmission to a macro eNB (MeNB) or a small cell eNB (SCeNB). As anexample, the WTRU may determine to attempt to take corrective actionusing the MAC instance associated with the small cell eNB. In anexample, the MAC instance to use for taking corrective action may beselected based on the relative timing between the MAC instances. Forexample, the MAC instance associated with the earliest timing (e.g., orin another example the latest timing) may be selected for performing thecorrective action.

In an example, a WTRU may be provided with independent power controladjustments for one or more (and/or each) of PUCCH, PUSCH and/or SRSthat are associated with a given MAC instance. Each MAC instance mayutilize power control commands that are independent of power controlcommands for other MAC instances at the WTRU. Each received powercontrol command may be associated with a given channel of a given MACinstance (e.g., and/or a specific instance of the channel if the MACinstance is associated with multiple channels of a given channel type).For example, if a given MAC instance is associated with a PUCCH, one ormore PUSCHs (e.g., where a PUSCH is associated with a correspondingcomponent carrier of a serving site for the MAC instance), and/or one ormore SRS transmissions (e.g., where an SRS transmission is associatedwith a corresponding component carrier of a serving site for the MACinstance), the WTRU may receive a power control commands that areassociated with one of the channel types of a specific MAC instance. Forexample, the WTRU may receive a first power control command for thePUCCH associated with the MAC instance, a second power control commandassociated with one or more of the PUSCHs of the MAC instance (e.g.,possibly a separate power control command for each PUSCH), and/or athird power control command associated with one or more of the SRStransmissions for the MAC instance (e.g., possibly a separate powercontrol command for each SRS transmission). In an example, the identityof the MAC instance that a received power control adjustment isapplicable to may be determined based on the identity of the MACinstance used for to receive the DCI that included the corresponding TPCcommand field.

In an example, power control for a given channel type may be commonacross multiple MAC instances. For example, a single power controlcommand may be used to adjust the power of PUCCH, PUSCH and/or SRStransmissions associated with different MAC instances. If the WTRUreceives a power control adjustment for a given channel, the powercontrol adjustment may be applied to any and/or alloccurrences/instances of the given channel for one or more (and/or all)MAC instances of the WTRU. For example, a WTRU may receive a powercontrol command for the PUCCH (e.g., via a first MAC instance), and theWTRU may adjust the transmit power for one or more (and/or all) PUCCHsassociated with the MAC instance over which the command was receivedand/or one or more (and/or all) MAC other MAC instances maintained bythe WTRU. A power control adjustment that may be applicable to channelsassociated with different MAC instances may be referred to as a globalpower control command/adjustment. Global power control commands may beused in combination with power control commands that are specific togiven MAC instance. For example, a field in the DCI used to send thepower control command (e.g., via a PDCCH of one or more MAC instances)may be used to indicate to the WTRU whether the power control command isa global power control command or a power control command that isspecific to a given MAC instance (e.g., the MAC instance over which thepower control command was received).

The WTRU may be configured to receive power control adjustments/commandsusing DCI Format 3. In an example, the WTRU may be configured withmultiple TPC RNTIs in order to determine which channel a given powercontrol command is applicable to. For example, the WTRU may beconfigured with one or more of a TPC-PUSCH-RNTI that may be used forencoding/decoding power control commands for the PUSCH, a TPC-PUCCH-RNTIthat may be used for encoding/decoding power control commands for thePUCCH, and/or a TPC-SRS-RNTI that may be used for encoding/decodingpower control commands for SRS transmissions. In an example, the WTRUmay be configured with multiple TPC RNTIs for each MAC instance. Forexample, the WTRU may have a first set of one of more TPC RNTIs (e.g.,one or more of a TPC-PUSCH-RNTI, a TPC-PUCCH-RNTI, a TPC-SRS-RNTI, etc.)for receiving power control adjustments for a first MAC instance, asecond set of one of more TPC RNTIs (e.g., one or more of aTPC-PUSCH-RNTI, a TPC-PUCCH-RNTI, a TPC-SRS-RNTI, etc.) for receivingpower control adjustments for a second MAC instance, and so forth. Inthis manner, a TPC command applicable to any of the channels for any MACinstance may be transmitted by the network using any MAC instance. Forexample, a power control command for the PUCCH of a first MAC instancemay be sent to the WTRU using a second MAC instance by encoding the DCIincluding the power control command with the TPC-PUCCH-RNTI associatedwith the first MAC instance. In another example, the MAC instance forwhich a given power control command is applicable may be used totransmit the DCI including the power control command and the WTRU may beconfigured to associate a given power control command with the MACinstance over which the power control command was received.

The timing of the subframe for which a given power control command isapplicable may be explicitly signaled and/or implicitly determined bythe WTRU. In an example, a power control command may be applicable to atransmission to occur in a subframe that is a predetermined amount oftime ahead of the subframe in which the power control command wasreceived. For example, if a power control adjustment was received insubframe(n), the power control command may be valid a UL transmission(e.g., on a channel for which the power control command was received)for any MAC instance in subframe(n+k) and beyond, where k may be apreconfigured number of subframes. For example, DCI included in a PDCCHtransmission associated with a first MAC instance may be received insubframe(n). The DCI may indicate a power control adjustment for SRS. Insubframe(n+k), SRS may be scheduled for one or more MAC instances, forexample a second MAC instance. The WTRU may determine to apply the powercontrol command received in subframe(n) of the first MAC instance to thetransmission of SRS in subframe(n+k) via the second MAC instance. Thus,the power control adjustment received in subframe(n) may be valid eventhough the MAC instance used for transmission of the DCI that includedthe power control command may be different than that used fortransmitting in the uplink. Such a scheme may be used when SRS may beused by multiple reception points in the network (e.g., multiple servingsites).

In an example, in order to facilitate the reception of power controlcommands that are applicable to a single MAC instance (e.g., and/or asingle channel type of a single MAC instance) via any MAC instancemaintained by the WTRU, the power control adjustment may include anindex that is used to explicitly indicate which MAC instance the powercontrol command is applicable to. For example, the indication (e.g.,index) of which MAC instance a power control adjustment is applicable tomay be received with the power control command in the DCI via any MACinstance. The indication may also specify what channel the power controlcommand is applicable to. In this manner, any MAC instance may be usedto adjust the power of a transmission to be performed using another MACinstance.

Although multiple MAC instances may be associated with independentschedulers, multiple MAC instances may use the same physical layertransceiver and/or resources. For example, OFDMA transmission schemesmay be used by multiple serving sites for downlink transmissions to theWTRU, and/or SC-FDMA transmission schemes may be used by multipleserving sites for receiving uplink transmissions from the WTRU.Transmission and/or reception of physical channels associated withdifferent serving sites (e.g., and/or or sets of serving sites) mayconflict with each other if the physical channels associated with thedifferent serving sites are used in an unrestricted manner. For example,a WTRU may receive a first scheduling grant for transmitting a PUSCHtransmission to a first serving site (e.g., using a first MAC instance)and a second scheduling grant for transmitting a PUSCH transmission to asecond serving site (e.g., using a second MAC instance). Each of thereceived grants may indicate that the WTRU is to transmit at the sametime using the same frequency resources. Simultaneous transmission oftwo PUSCH transmission in the same subframe and using the same resourceblock allocation may be infeasible for a variety of reasons.

Various examples disclosed herein may enable concurrent transmissionand/or reception of physical channels associated with different servingsites. It should be understood that different examples may be used invarious combinations, for example based on one or more of the differenttypes of subframe timing between the serving sites, the different typesof subframes used at serving sites, the time/frequency resourcesassociated with transmissions to and/or from the different servingsites, the relative level of coordination between the serving sites, thetype of physical channel(s) being transmitted to and/or from thedifferent serving sites, and/or the like.

For example, in the uplink a WTRU may be configured to transmit multipleUL transmissions to multiple serving sites. For example, the WTRU mayprovide concurrent physical channel access to multiple MAC instancesthat are associated with transmissions to different serving sites. TheWTRU may be configured using higher layer signaling (e.g., RRCsignaling) regarding whether UL transmission to multiple serving sitesare allowed. For example, RRC may be used to configure the ability totransmit data and/or uplink control signaling to multiple sites in thesame or different subframes. He WTRU may be configured with a respectiveset of UL transmission parameters for transmission to each of theserving sites. For example, each serving site/MAC instance may beassociated with one or more of power control parameter(s), timingadvance parameter(s), cell ID(s) (and/or virtual cell ID(s)), etc. thatare specific to a given serving site and/or MAC instance.

As an example of UL concurrent UL transmission to independentlyscheduled serving sites, consider a WTRU that is configured with atleast two radio bearers. A first radio bearer may be associated with afirst set of QoS parameter(s) and may be associated with transmissionsto a first serving site. A second radio bearer may be associated with asecond set of QoS parameter(s) and may be associated with transmissionsto a second serving site. For example, the WTRU may transmit ULdata/traffic to the first serving site using the first radio bearer,while transmitting UCI associated with DL transmission received from thesecond serving site (e.g., CSI reports, HARQ feedback, etc.) to thesecond serving site using the second radio bearer. In another example,the WTRU may be configured to transmit multiple sets of UCI, for examplea first set of UCI to the first serving site and a second set of UCI tothe second serving site. In either case, if UL transmission is to besupported for concurrent transmission to multiple serving sites, theWTRU may be configured to perform contention resolution for the physicallayer resources between the MAC instances associated with thetransmission to the different serving site. As an example, the WTRU maybe configured to use one or more of time segregation of physical layerresources, frequency segregation of physical layer resources, and/orcode segregation of physical layer resources in order to supportconcurrent transmission to multiple serving sites.

When used herein the term concurrent transmission to multiple servingsites may refer to one or more of simultaneous transmission to multipleserving sites at the same time (e.g., transmitting to multiple servingsites in the same subframe using the same and/or different frequencyresources), transmission to multiple serving sites using the samefrequency resources within a specified amount of time (e.g.,transmitting to multiple transmissions to different serving sites usingthe same frequency within a relatively close amount of time and/orduring the same RRC Connected session), and/or the like. Concurrenttransmission to multiple serving sites may refer to the scenario whereinany one of multiple serving sites may have the ability to schedule theWTRU for transmission on the same time/frequency resources as are usedby a different serving site. Thus, concurrent transmission may refer tothe chance that a WTRU may receive conflicting scheduling requests frommultiple serving sites.

In an example, UCI for multiple serving sites may be transmitted to oneof the serving sites, for example via the PUCCH associated with one ofthe serving sites. For example, first control information applicable toa first serving site may be included a PUCCH transmission to the firstserving site, and second control information applicable to a secondserving site may be included in the PUCCH transmission to the firstserving site. The control information may be HARQ ACK/NACK information,for example if the WTRU has determined that HARQ feedback is to beprovided to multiple serving sites in the same subframe. The PUCCHparameters used for a transmission that includes UCI applicable tomultiple serving sites may be a preconfigured set of parametersconfigured specifically for transmitting control information formultiple serving sites to a single site. For example, the parametersused for PUCCH transmissions containing control information applicableto multiple serving sites may depend on the subframe in which the PUCCHis transmitted. In an example, one of the serving sites may bedesignated as the serving site to which UCI is transmitted. The PUCCHparameters may be configured by the serving site that receives the UCIfor the multiple sites. A set of reception points (RPs) may beconsidered to be from a same serving site. Multiple sets of RPs may beconsidered to be from different serving sites (e.g., with one set of RPsper serving site).

One example method for segregating physical channel resources fortransmissions to multiple serving sites may be for the physical layerentity to serve a single MAC instance (e.g., where each MAC instance isassociated with a different serving site) at any given instance in time.In such a scenario, a physical channel associated with a single MACinstance may be allowed to be used in a given subframe. Which MACinstance may utilize the physical channel(s) in a given subframe may bedetermined according to semi-static configurations and/or dynamicallybased on explicit signaling and/or implicit criteria. For example,priority information for the MAC instances may be utilized to resolveconflicts between a plurality of MAC instances.

As an example, in order to support concurrent transmission to multipleserving sites, the WTRU may be configured to implement a timesegregation scheme (e.g., time division multiplexing (TDM)) for the ULtransmissions to the multiple serving sites. For example, a givensubframe may be dedicated for transmissions to a specific serving site.The WTRU may be configured with a subset of subframes for transmittingto each of the different serving sites. The WTRU may be configured witha set of UL transmission parameters (e.g., power control parameters, setof virtual cell IDs, dedicated PUCCH resources, etc.) for each site. TheWTRU may determine which set of UL transmission parameters to applybased on the subframe subset that includes the subframe in which the ULtransmission is to occur. For example, even numbered subframes may beinclude in the subframe subset of a first serving site. Odd numberedsubframes may be included in the subframe subset of a second servingsite. For UL transmissions occurring in even numbered subframes, theWTRU may determine to apply to UL transmission parameters associatedwith the first serving site. For UL transmissions occurring in oddnumbered subframes, the WTRU may determine to apply to UL transmissionparameters associated with the second serving site.

In an example, each physical channel and/or transmission type may betransmitted to a different serving site. For example, PUCCH may betransmitted to a first serving site and PUSCH may be transmitted to asecond serving site. To allocate physical resources for transmission ofmultiple UL channels that are associated with different serving sites,each channel (e.g., channel type) may be assigned a subset of subframesthat may be used for transmission of the channel to its correspondingserving site. In such a scenario, the WTRU may determine which ULtransmission parameters to apply based on the type of channel and/ortype of transmission being sent in the subframe. In an example,different types of transmissions may be allocated subframe subsets. Forexample, CQI transmissions may be allocated a first subset of subframesand SRS transmissions may be allocated a second subset of subframes.

Multiple sets of subframe subsets may be orthogonal to each other (e.g.,non-overlapping in the time domain) and/or may be configured to overlap.For example, if two or more subframe subsets associated with differentserving sites overlap, multiple UL transmissions to different servingsites may occur in the same subframe(s). For example, a WTRU may beconfigured to transmit a PUCCH transmission to a first serving site anda PUSCH transmission to a second serving site in the same subframe. Asan example, the WTRU may receive an UL grant for transmission to a firstserving site in subframe(n), and the WTRU may also be configured totransmit HARQ feedback via the PUCCH to a second serving site in thesame subframe(n). As another example, the WTRU may be configured totransmit HARQ feedback to multiple serving sites in the same subframe.In another example, the WTRU may utilize overlapping subframe subsetsfor transmitting power headroom reports (PHRs) to multiple serving sitesin the same subframe.

In an example, in order to segregate the subframe subsets associatedwith different serving sites, one or more HARQ feedback timing rules maybe modified. For example, it may be desirable to avoid transmitting aPUSCH transmission to a first serving site and HARQ feedback to a secondserving site in the same subframe. However, the WTRU may have recentlyreceived a PDSCH transmission from the second serving site (e.g., foursubframes ago), and legacy HARQ timing rules may have dictated that theWTRU is to transmit the HARQ feedback in the same subframe as the WTRUwas granted UL transmission resources for a PUSCH transmission to thefirst serving site. To avoid this scenario, the WTRU may indicate to oneor more of the serving sites that the WTRU is utilizing multi-servingsite operation. The indication of multi-serving site operation mayinclude an indication of the subframe subsets that are applicable to thedifferent serving sites (e.g., and/or physical channels). Upon receivingthe indication that the WTRU is utilizing multi-serving site operation(e.g., and/or the indication of the different subframe subsets), aserving site may indicate a different subframe offset to be used forHARQ timing (e.g., a subframe offset different than four) by the WTRUfor acknowledging PDSCH transmissions from that serving site.

The WTRU may be configured with multiple subframe subsets to use fortransmissions to different serving sites in a variety of ways. Forexample, higher layer signaling (e.g., RRC signaling) may be used toconfigured to the WTRU with the subframe subsets. The high layersignaling may be received from any of the serving sites. For example, afirst serving site may configure the subframe subsets to be used for thefirst serving site and a second subframe subset to be used with a secondserving site. In an example, physical layer signaling may be used toindicate a subframe subset to the WTRU. For example, the WTRU mayreceive a UL grant using DCI Format 0/4 on the PDCCH, and the DCI mayindicate the subframe subset pattern that a WTRU may use for that site.

In an example, upon sending a SR and/or other control signaling, a WTRUmay indicate a preferred density (and/or ratio) of subframes that theWTRU requests to be included in the subframe subset for the serving site(e.g., a percentage of subframes to be allocated for use transmitting tothat site). Rather than or in addition to a subframe density, the SRand/or other control signaling may indicate a preferred subframe subsetpattern that the WTRU is requesting for the serving site. Thenetwork/serving site may confirm and/or reject the request densityand/or pattern. The network/serving site may propose a different densityand/or subframe subset pattern. The network may indicate the densityand/or pattern of subframes assigned to the WTRU when transmitting an ULgrant on DCI Format 0/4 to the WTRU (e.g., and/or when transmittinganother type of DCI). If the WTRU has already been allocated a subset ofsubframes for use at another serving site, the WTRU may indicate itscurrent subframe subset pattern for the other site(s) to a serving sitefrom which the WTRU is requesting a new subframe subset. Rather than orin addition to sending an indication of its current subframe subsetpattern associated with other serving site(s) when requesting a subframesubset from a different serving site, the WTRU may indicate to thedifferent serving site that it is currently configured for ULtransmission with another site during the subframe subset request (e.g.,by identifying the other serving sites by serving site ID and/or cellID). Such an indication may trigger the different serving sites toexchange information related to the current subframe subsets and/ornegotiate a new subframe subset for one or more of the serving sites(e.g., over X2, X2bis, or any other interface between the two servingsites).

If the WTRU determines that more or fewer subframes should be allocatedto the subframe subset of a given serving site, the WTRU may send amessage to the serving site requesting modification of the subframesassigned to the subframe subset for that serving site. The WTRU may senda request to modify the subframe subset for a given serving site to theserving site with the subframe subset to be modified and/or to adifferent serving site. For example, if the WTRU determines that a largeamount of data (e.g., greater than a threshold) is buffered fortransmission on a logical channel to be transmitted to a given servingsite, the WTRU may determine to request additional subframes be added tothe subframe subset associated with that serving site. The request maybe transmitted to the serving site with the subframe subset to bemodified and/or to a different serving site. The WTRU may transmit abuffer status report and/or an indication of the QoS for one or more(and/or all) UL radio bearers when requesting subframe subsetmodification. The buffer status report and/or QoS information may besent to the network when initially requesting a subframe subset and/orperiodically/intermittently in order for the network to determinewhether to configure the WTRU with subframe subset(s). The network(e.g., one or more serving sites) may used the buffer status reportand/or QoS information in order to configure and/or reconfigure thesubframe subsets accordingly.

A given serving site may be configured with one or more potentialsubframe subset. The serving site may indicate the potential subframesubsets to be used in a cell of the serving site using broadcastsignaling such as the master information block (MIB) or a systeminformation block (SIB). The WTRU may attempt to access a cell of theserving site using a RACH procedure in subframe within a subframe subsetthat the WTRU wants to use in the cell. For example, a SIB broadcast inthe cell may indicate a first subframe subset includes subframesnumbered 0-4 and a second subframe subset includes subframes numbered5-9. If the WTRU attempts to perform RACH during subframe 5 (e.g.,and/or 6-9), the WTRU may be implicitly requesting to be assigned to thesubframe subset that includes subframes numbered 5-9. In an example asemi-static configuration including or more subframe subsets may beprovided to the WTRU by higher layer signaling (e.g., RRC signaling).The higher layer signaling used to configure the subframe subset of agiven serving site may be transmitted from that serving site and/or froma different serving site. In an example, if the WTRU is configured witha DL subframe subset (e.g., a set of subframes in which the WTRU mayreceive DL transmissions), the WTRU may implicitly determine the ULsubframe subset pattern for the serving site based on the assigned DLsubframe subset pattern. For example, the UL subframes may be the sameas the DL subframes and/or the DL subframe subset may be mapped to acorresponding UL subframe subset.

A configuration of a subset of subframes may also be referred to as asemi-static time division multiplexing (TDM) scheme. For example, a MACinstance may be configured semi-statically through RRC signaling toutilize physical channels in the UL according to a received TDMconfiguration. As an example, the TDM configuration may include a bitmapthat is indicative of the subframes that are assigned to the WTRU aspart of the TDM configuration. The bitmap may include a plurality ofbits that each represent a subframe and/or frame which may be utilizedby a MAC instance for UL transmissions. For example, a first bit mayrepresent a first subframe or frame, and a 1 may indicate that the firstsubframe or frame is assigned to the WTRU as part of its subframesubset, while a 0 may indicate that the first subframe or frame is notassigned to the WTRU as part of its subframe subset. The bitmap may bespecific to a certain MAC instance and/or may be specific to a certainphysical channel of the MAC instance. The bits of the bitmap may eachcorrespond to a plurality of subframes, for example subframes in arepeating pattern. For example, a first bit may recommend a firstsubframe of each frame in the UL. The bitmap may be used for assigningsubframes for UL and/or DL transmission to a serving site. In anexample, the bitmap may be used to indicate which MAC instance a givensubframe is associated with. For example, a first bit of the bitmap maybe indicative of whether the subframes associated with the bit (e.g.,identified with a subframe number and/or frame number) are associatedwith a first MAC instance or a second MAC instance. The bitmapconfiguration may be indicative of a pattern of subframe usage. Forexample, the series of bits of the bitmap may represent a plurality ofsets of predetermined subframe subsets. The WTRU may indicate to thenetwork/serving site a preferred subframe subset, for example using thebitmap. In an example, the TDM configuration may be indicated as one ofset of predefined TDM subframe configurations. The predefined subframeTDM configuration(s) may establish for each subframe whether thesubframe is used by a first MAC instance or by a second MAC instance.Such configuration may also indicate certain subframes where certainsymbols of a subframe are not used for transmission for any MAC instance(e.g., a transmission gap), for instance in case the WTRU is to switchfrom one MAC instance to another.

The WTRU may determine which site to transmit UCI to and/or when totransmit UCI based on the assigned TDM configuration (e.g., subframesubset configuration). For example, which subframe to use fortransmitting UCI may be determined based on the identity of the MACinstance assigned to the subframe and/or the identity of the MACinstance that is associated with the UCI. For instance, the WTRU maydetermine the maximum number of PDSCH transmissions for which HARQfeedback is to be provided (e.g., on PUSCH and/or PUCCH) in a subsequentsubframe based on the assigned TDM configurations for the different MACinstances. If the WTRU determines that more feedback is to be providedin a given subframe than its assigned resources may support (e.g., UCIis to be provided to both a first serving site and a second serving sitein a subframe assigned to only the first serving site), the WTRU maydetermine to multiplex and/or otherwise bundle the UCI/feedback andtransmit the bundled UCI/feedback to the single assigned serving site.

In an example, rather than or in addition to being assigned a subframesubset for transmitting to different serving site, the WTRU may beconfigured to perform dynamic WTRU-autonomous selection of which servingsite to transmit to in a given subframe based on a relative prioritybetween MACs instances. For example, the WTRU may not be assigned asubframe subset (e.g., the WTRU may be scheduled for transmission by aplurality of MAC instances in a given subframe) and/or the WTRU may beassigned subframe subsets wherein the subsets assigned to two or moreMAC instances/serving sites may overlap for one or more subframes. Insuch a scenario, the WTRU may determine which serving site to transmitto dynamically based on the type of data being transmitted and/orpriority information associated with the plurality of serving sites. Forexample, the WTRU may be configured to utilize a preemption-basedapproach where a particular MAC instance or serving site (e.g., a MACinstance that corresponds to a macro eNB) may have absolute priorityover one or more other MAC instances or serving sites. If absolutepre-emption is utilized, each MAC instance may be assigned a prioritylevel that may be different than the priority level assigned to otherMAC instances. If a higher priority level MAC instance is scheduled fortransmission in the same subframe as a lower priority level MACinstance, the higher priority MAC instance may be allowed to use of thephysical channel (e.g., such as transmitting over PUCCH and/or PUSCH;receiving from a downlink control channel, etc.) during the subframe andthe transmission for the lower priority channel may be dropped and/ortransmitted via the higher priority MAC instance. In an example, a lowerpriority MAC instance may be permitted to use of a physical channels ina given subframe if a higher priority MAC instance is not in Active Timein this subframe. Additional priority rules may be utilized rather thanor in addition to an absolute priority between MAC instances. Forexample, the type of data being transmitted, the identity of the logicalchannel associated with the transmission, and/or other criteria may beused to determine which MAC instance should be allowed to transmitherein.

In scenarios where the use of one or more physical channels is denied toa MAC instance due to contention (e.g., a higher priority MAC instanceis utilizing physical layer resources in a given subframe), the WTRU maysend an indication to the serving site corresponding to the MAC instancefor which resources were denied (e.g., the lower priority MAC instance).The indication may include identifying information for the MAC instancethat was prioritized of the MAC instance receiving the indication and/ormay indicate one or more (and/or all) of the subframes assigned to thehigher priority MAC instance and/or other higher priority MAC instancesutilized by the WTRU. For example, a field in one or more of physicallayer signaling (e.g., a PUCCH transmission and/or a PUSCHtransmission), MAC layer signaling (e.g., a MAC CE), and/or RRCsignaling in order to indicate the identity of the subframe that was thesubject of contention and/or the identity of the MAC instance/servingcell that was prioritized. The WTRU may retransmit the information thatwould have been transmitted to the serving site that was deniedtransmission resources in a subframe in a subsequent available set ofresources for that serving site. The indication regarding the denial ofresources (e.g., perhaps with an indication of the MAC instance/servingsite that was prioritized) may be included in the subsequenttransmission. The subsequent available set of resources may be the firstset of resources available for transmitting to the denied serving site(e.g., RACH) after the contention. In an example, the subsequentavailable set of resources may be the first set of subsequent ULresources that are scheduled for the WTRU (e.g., with a new UL grant),after the subframe during which the contention occurred.

The WTRU may be provided/scheduled with a different set of resources forthe transmission of information included in messages that have beendropped due to contention. For example, a WTRU may be configured with analternate set of PUCCH resources to use when a PUCCH transmission hasbeen dropped due to the MAC instance associated with the PUCCHtransmission being of a lower priority.

In some scenarios, DL transmissions and UL transmissions associated withone or more MAC instances may be time duplexed (e.g., time divisionduplexing (TDD)) while DL transmissions and UL transmissions associatedwith one or more other MAC instances (e.g., MAC instances associatedwith another frequency band) may be frequency duplexed (e.g., frequencydivision duplexing (FDD)). In such scenarios, the TDD and/or FDDscheme(s) may be configured by the network (e.g., the one or moreserving sites) such that UL physical channels associated with a FDD MACinstance may be available in subframes where UL transmission does nottake place for one or more (and/or all) TDD MAC instances. For example,the UL physical channels associated with a FDD MAC instance may beavailable in subframes reserved for DL transmission with respect to theone or more (and/or all) TDD MAC instance(s).

In order to switch the physical layer parameters in accordance with theconfigurations provided by the different MAC instances, the WTRU may beallowed a certain period of time in order to switch between thetransmission (and/or reception) for a first MAC instance to that of asecond MAC instance. To accommodate the switching time, the lastsubframe available to a given MAC instance before a change to anotherMAC instance may be shortened. For example, the WTRU may be configuredsuch that no transmission (and/or reception) is performed on the last N₁symbols of the subframe. If N₁ is equal to 1, shortened transmissionformats may be used. For example, one or more shortened PUCCH formatsmay be used. As an example, one or more shortened PUCCH formats similarto the shortened format for transmitting PUCCH with SRS transmission inthe last symbol of the subframe may bed used. In an example, rather thanor in addition to shortening the final subframe before the transition,the first subframe after the transition may be shortened. For example,the first N₂ symbols of the first subframe after a change may beunavailable to the newly active MAC (e.g., for transmission and/orreception). Whether the subframe that is shortened is the subframe priorto the switch and/or the subframe subsequent to the switch may depend onone or more priority rules between the MAC instances.

In some deployments, different serving sites may utilize asynchronoussubframe timing. For example, a first serving site associated with afirst layer may begin its subframes at a different time than a secondserving site associated with a second layer begins its subframes (e.g.,a MeNB associated with a Macro layer utilizes different timing alignmentthan a SCeNB associated with a Pico layer). In another example, one ormore cells within a single layer (e.g., associated with a single servingsite) may not be time synchronous. If different serving sites operateusing asynchronous subframe timing, the MAC instances associated withthe different serving sites may have different subframe number offsets.For example, subframe 0 of a given frame in a cell associated with afirst serving site may occur during subframe 1 of a frame in a cellassociated with a second serving site. Additionally, the start of thesubframes for different serving sites may occur at different times. Forexample, a first subframe associated with a first serving site may startat a different time than a subframe of a second serving site, but thetwo subframes may partially overlap in time (e.g., one or more symbolsfor the different subframes may overlap).

If multiple serving sites are not symbol-aligned, time segregation(e.g., a TDM configuration) may still be used. For example, in order toavoid overlapping subframes when the different serving sites are notsymbol-aligned, a WTRU may be configured with subframe subsets for thedifferent serving sites that do not include adjacent subframes. The WTRUmay recommend subframe subsets to one or more of the serving sites inorder avoid being assigned subframes that may have symbol overlap withthe subframes assigned to a different serving site. In an example,rather than omitting entire subframes near the transition from asubframe subset in the case on non-symbol aligned serving sites, thesubframes may be assigned in an overlapping manner. For example,consider a plurality of symbols that may be used in subframes of aplurality of serving sites (e.g., for purposes of explanation, assumethe symbols are numbered 0-52, for example from the perspective of cellA of a first serving site). A WTRU may be configured to transmit/receivefor the cell A of a first serving site during a first subframe (e.g.,including symbols 0-13), a second subframe (e.g., including symbols14-27) and a third subframe (e.g., including symbols 28-41). The WTRUmay also be configured to transmit/receive for a cell B of a secondserving site during a first subframe (e.g., that overlaps with symbols11-24 of cell A), a second subframe (e.g., that overlaps symbols 24-38of cell A), and a third subframe (e.g., that overlaps symbols 39-52 ofcell A). Cell A may be prioritized over cell B such that if cell A usesits first subframe, then cell B may be unable to use its first subframe,although cell B may still be used for its second subframe (e.g., and/orits first subframe if cell A does not schedule the WTRU).

If a WTRU is assigned a plurality of partially colliding subframesubsets, the WTRU may send an indication to one or more of the servingsites requesting modification of one or more of its currently configuredsubsets. In an example, the WTRU may indicate to one or more servingsites a symbol offset representing the difference in symbol timingbetween the serving sites. The serving sites may use the offsetinformation to perform subframe set configuration and/orreconfiguration.

In an example, new types of subframes may be assigned to the WTRU, forexamples subframes with a different number of symbols per subframe. Themodified subframes may have fewer than 14 symbols, allowing the TDMconfiguration to avoid overlap in the case of partially overlappingsubframes. Encoding (e.g., using rate-matching) may be used by the WTRUin the case of shortened and/or elongated subframes to allow for properdecoding at the receiver, and the network may be aware of which symbolsare unused based on the subframe configuration and/or may be informed ofwhich symbols are to be dropped by the WTRU.

In some scenarios, a normal or extended cyclic prefix may be used toaccount for the overlapping timing between subframes of different MACinstances. However, in other scenarios the overlap may not be properlyhandled by either normal or extended cyclic prefix. Instead, one or moresymbols from one or more of the overlapping subframes may be dropped toensure proper operation. The location of the dropped symbol(s) (e.g., afirst symbol of physical resource block (PRB); the last symbol of a PRB;multiple symbols of a PRB, etc.) may depend on the identity of the MACinstance associated with the subframe for which the symbol(s) weredropped. For example, priority rules may be used to determine which MACinstance drops a symbol in case overlap. In an example, the last symbolof the earlier subframe may be dropped. For example, if there is asubframe collision between two MAC instances, then the MAC instance thatis configured to transmit in the earlier starting subframe may drop oneor more symbols at the end of its subframe (e.g., the last symbol). Inan example, the first symbol of the later subframe may be dropped. Forexample, if there is a subframe collision between two MAC instances,then the MAC instance that is configured to transmit in the laterstarting subframe may drop one or more symbols at the beginning of itssubframe (e.g., the first symbol).

If the last symbol of a given subframe is to be dropped in order toavoid transmission overlap, the resource element (RE) mapping may beperformed for the transport block including the dropped symbol in amanner similar to how the RE mapping is performed when SRS istransmitted on the last symbol of a transmission. If the first symbol ofa subframe is being dropped, the RE mapping may be performed for thetransport block including the dropped symbol in a manner similar to howthe RE mapping is performed when SRS is transmitted on the last symbolof a transmission, although the data may be mapped to later adjacentsymbol (e.g., the data that would be mapped to symbol 0 if SRS wastransmitted in the last symbol of the subframe may be mapped to symbol 1instead, the data that would be mapped to symbol 1 if SRS wastransmitted in the last symbol of the subframe may be mapped to symbol 2instead, etc.). If SRS transmission is scheduled for a subframe whereoverlap occurs, the WTRU may determine to drop the SRS transmission. Inan example, if the last symbol of a subframe is dropped in the case ofoverlap and SRS is also scheduled in an overlapping subframe, ratherthan dropping the SRS, the data associated with the second to lastsymbol may be dropped while SRS is transmitted on the second to lastsymbol of the subframe (e.g., the last symbol used for transmission bythat MAC instance as the final symbol may be dropped due to overlap).

The WTRU may be configured to indicate when one or more symbols havebeen dropped due to subframe overlap. For example, the indication may besent to the serving site associated with the transmission including thedropped symbol and/or to the serving site associated with thetransmission that led to a symbol being dropped in a differenttransmission. The WTRU may include a reason for the dropped symbol, forexample overlap with another transmission. In an example, if thetransmission including the dropped symbol is a PUSCH transmission, theWTRU may include an indication of the dropped symbol in the PUSCHtransmission. The indication may be included in a flag for the PUSCHtransmission. The serving site/eNB may be configured to attempt toblindly decode the PUSCH transmission in order to determine whether ornot a symbol may have been dropped. For example, the eNB may firstattempt to decode a PUSCH transmission assuming a symbol was dropped. Ifthe eNB detects the flag indicating that the symbol was dropped, it maycontinue to attempt to decode the PUSCH transmission assuming a droppedsymbol. If the flag is not decoded and/or the PUSCH transmission was notsuccessfully decoded assuming a symbol was dropped, the eNB may attemptto decode the PUSCH transmission as if a symbol was not dropped.

In an example, a WTRU may include a request to use reduced symboltransmission in a service request indication sent to a serving site. Forexample, a WTRU may include a list of subframes and/or an indication ofwhich subframes it is requesting to use a reduced number of symbols for.

In an example, a WTRU may semi-statically indicate (e.g., via RRCsignaling) a list of subframes where a symbol (e.g., first, last, etc.)may be dropped. The indication may be specific to each MAC instance. Forexample, the WTRU may send a first message/indication to a first servingsite associated with a first MAC instance that indicates a firstplurality of subframes which may be used for reduced symboltransmissions, and a second message/indication to a second serving siteassociated with a second MAC instance that indicates a second pluralityof subframes which may be used for reduced symbol transmissions. Theindication may also be transmitted using MAC and/or physical layersignaling.

In an example, a WTRU may indicate to the network (e.g., one or moreserving sites) that there may be overlap in some subframes between twoMAC instances. The network may determine which MAC instance(s) may dropsymbols and may configure the WTRU with such information. For example,the eNBs associated with the different serving sites may negotiate whichMAC instance(s) should be utilized for dropping symbols. The WTRU mayprovide a list and/or indication of possible subframes where such anoverlap may occur. The determination of which MAC instance may expect adropped symbol may be performed by a centralized control entity and/orat one or more of the serving sites. For example, the different servingsites may communicate via an X2 interface to determine which of theserving sites should expect one or more transmissions with droppedsymbols. In an example, the indication that a symbol may be dropped(e.g., and perhaps an indication of which symbol(s) may be dropped) maybe provided to the WTRU in DCI including a UL grant. For example, afield in the UL grant may indicate the grant is for a transmission witha dropped symbol(s) and may specifically indicate which symbol(s) shouldbe dropped.

In an example, the WTRU may autonomously determine which MAC instance(s)should expect a dropped symbol in a DL transmission and/or should drop asymbol in the uplink. The determination of which transmission should beused to drop a symbol may be based on one or more factors such as theQoS associated with data included in the transmission, buffer status forone or more logical channels associated with the transmission, apriority order between MAC instance, etc. After determining which MACinstance(s)/serving site(s) should use dropped symbols for one or moretransmissions, the WTRU may then indicate to the appropriate servingsite that in future UL grants, the MAC instance at the serving site mayassume a reduction of symbols in an indicated set of subframes.

In an example, physical channels for more than one MAC instance/servingsite may be used for transmissions in the same subframe. As an example,physical channels associated with different MAC instances may be used inthe same subframe if the transmission/reception of the physical channelsoccurs in different frequency channels and/or frequency bands (e.g., afirst physical channel associated with a first MAC instance istransmitted to a first serving site in a first frequency band, and asecond physical channel associated with a second MAC instance istransmitted to a second serving site in a second frequency band). In anexample, physical channels associated with different MAC instances maybe used in the same subframe if the transmission/reception of thephysical channels occurs in different resource blocks (e.g., a firstphysical channel associated with a first MAC instance is transmitted toa first serving site in a first resource block, and a second physicalchannel associated with a second MAC instance is transmitted to a secondserving site in a second resource block). In an example, physicalchannels associated with different MAC instances may be used in the samesubframe if the transmission/reception of the physical channels involvestransmission of different types of physical channels (e.g., PUCCH forone serving site and PUSCH for another serving site). In an example,physical channels associated with different MAC instances may be used inthe same subframe if the transmission/reception of the physical channelsmay be separated using one or more transmission properties (e.g., covercode for PUCCH, orthogonal DM-RS, etc.).

As an example, frequency segregation may be performed in order totransmit to multiple serving sites in the same subframe. Frequencysegregation may be used in addition to time segregation and/or withouttime segregation. For example, if a partially overlapping timesegregation scheme is utilized, frequency segregation may also beutilized, for example for subframes for which there is partial overlapand/or for all subframes. For example, a WTRU may be configured with oneof more frequency subband subsets for one or more serving sites. Forexample, ifs first cell of a first serving site operates in the samefrequency band and/or component carrier of a second cell of a secondserving site, the MAC instances associated with the different servingsites may be configured to use different subband subsets within thefrequency band/component carrier. In an example, the bandwidth (BW)utilized by the different serving sites may be divided into a pluralityof BW parts. Each serving site may be configured to utilize one or moreof the BW parts for communicating with the WTRU. For example, each BWpart may be treated as a component carrier in carrier aggregation. Forexample, each BW part may include corresponding PUCCH and PUSCHresources. Some bandwidth parts may include PUCCH without a PUSCH (e.g.,for CSI reporting to a serving site) and/or PUSCH without PUCCH.

One or more physical channels and/or types of transmission (e.g., PUSCH,PUCCH, SRS, etc.) may be configured with an RB offset. The RB offset mayrepresent a frequency guard and/or other type separation betweenfrequency bands used for transmitting to different serving sites. The RBoffset may ensure frequency segregation for UL transmissions destinedfor different serving sites. The RB offset may be configured by thenetwork (e.g., one or more of the serving sites) signaled to the WTRU.In an example, the WTRU may determine an RB offset for a given cellbased on the cell ID (and/or virtual cell ID) of cell being accessed ina given serving site.

A WTRU may be configured to transmit signals that span multiple BWparts. For example, a single SRS sequence may be transmitted over a fullBW of a cell and/or serving site, which may span a plurality of BWparts. In an example, a WTRU may transmit different SRSs (e.g., eachwith its own set of parameters) for each BW part.

The transmission power utilized by the WTRU may be specific to which BWpart is used for transmission. For example, a WTRU may be configuredwith an independent maximum transmit powers (e.g., P_(CMAX)) per BWpart. For example, the WTRU may be perform UL transmission power controlindependently for each BW part. In another example, the WTRU may beconfigured with a single maximum transmit power value (e.g., P_(CMAX))for the entire BW. For example, if the maximum transmit power isdetermined across the whole BW, the WTRU may first determine the powerto be utilized for PUCCH transmission in a given subframe, and may thenallocate remaining power below the maximum transmit power for usetransmitting the PUSCH. The PUCCH and PUSCH may be configured fortransmission using power control parameters that are specific to theserving site associated with the channel transmission.

If multiple PUCCHs are to be transmitted in a given subframe (e.g., afirst PUCCH transmission to a first serving site, a second PUCCHtransmission to a second serving site, etc.), a priority ranking for thePUCCHs and/or for the serving sites may be provided by higher layersignaling. For example, the WTRU may determine the transmission powerused for transmitting a highest priority PUCCH/serving site first, thendetermine the transmission power to be allocated to the next highestpriority PUCCH/serving site second, and so on. Once the PUCCHresources/transmission power for the serving sites used for PUCCHtransmission in the subframe have been allocated transmission powerlevels, the remaining power may be used for one or more PUSCHtransmissions. For example, if multiple PUSCH transmissions are tooccur, the power allocated for each transmission may be determined as ifthe WTRU has full transmission power (e.g., PUCCH is not transmitted),and the determined power levels may be scaled according to the powerremaining after the total PUCCH power level(s) has been assigned.

If the maximum transmit power is allocated across the entire BW used bythe WTRU (e.g., a single P_(CMAX) is used for the entire BW), a singlepower headroom report (PHR) may be reported by the WTRU for reportingpower information related to the entire BW. For the scenarios where WTRUis configured with an independent maximum transmit power (e.g.,P_(CMAX)) per BW part and/or carrier, the WTRU may be configured to sendPHRs per BW part and/or carrier. The PHR may be transmitted to one ormore of the serving sites. For example, the PHR for a given BW partand/or carrier may be reported the serving site associated withtransmissions sent from the WTRU over the given BW part and/or carrier.In another example, the PHR of a given BW part and/or carrier may bereported to a serving site that does not receive transmissions from theWTRU using that BW part and/or carrier. In an example, the PHR for agiven BW part and/or carrier may be reported to all serving sitesutilized by the WTRU. In another example, each serving site may receivePHRs for all of the BW parts and/or carriers used by the WTRU.

The WTRU may perform scaling of its transmissions. For example, if theWTRU is expected to perform uplink transmissions (e.g., on one or morePUCCH resource(s) and/or one or more PUSCH resource(s)) at the same time(e.g., in the subframe and/or over one or more overlapping symbols) to aplurality of serving sites, the WTRU may allocate transmission poweraccording to a priority. For example, transmissions corresponding to thedata path of a MeNB serving site may be prioritized over transmissionsfor a data path including an SCeNB serving site. For example, afterallocating power to the transmission associated with the MeNB servingsite, remaining power may be allocated for transmission to the SCeNBserving site.

A first serving site (e.g., and/or a first cell of a first serving site)may have a timing configuration that differs from another a secondserving site (e.g., and/or a second cell of a second serving site).Therefore, if the timing difference between the cells/serving sites isgreater than a predetermined threshold, frequency segregation may bedifficult to implement. Thus, the WTRU may determine the timingdifference between two cells/serving sites and check if the timingdifference is within a preconfigured range. If the timing difference iswithin the range the WTRU may determine that frequency segregation maybe utilized and may indicate that frequency segregation may be used tothe network (e.g., one or more of the serving sites). If the timingdifference is outside the preconfigured range, the WTRU may determinenot to use frequency segregation and may indicate that frequencysegregation may be used to the network (e.g., one or more of the servingsites). The WTRU may determine a timing advance value to be used insubframes where frequency segregation is configured by averaging thetiming advance values of each of the cells/serving sites for whichtransmission is performed. In another example, the WTRU may determine touse the largest timing advance value of the timing advance values ofeach of the cells/serving sites for which transmission is performed. Inanother example, the WTRU may determine to use the smallest timingadvance value of the timing advance values of each of the cells/servingsites for which transmission is performed. In another example, the WTRUmay determine to use the timing advance value associated with a highestpriority serving site/cell for transmissions to each of thecells/serving sites.

The WTRU may determine the configuration of the different BW partsand/or the network (e.g., one or more serving sites) may determine theconfiguration of BW parts. For example, the BW parts may be configuredin a manner similar to subframe subsets are configured for timesegregation. For example, any of the methods described herein forconfigured a subframe subset may be used for configuring a BW part for agiven serving site and/or set of serving sites.

The WTRU may allocate transmit power for the transmission of a pluralityof PUCCH transmission (e.g., to different serving site) in one or moreways. For example, the WTRU may be configured to allocate power based onthe total amount of power available in a given subframe. For example,the maximum transmit power (e.g., P_(CMAX)) may represent themaximum/total transmit power that may be used for transmissions by theWTRU (e.g., within a given subframe). The WTRU may be configured toevenly divide the maximum transmit power among a plurality of PUCCHtransmissions to different serving sites. For example, the WTRU maydetermine a value P_(CMAX,c), which may represent the maximum WTRUoutput power. The WTRU may divide P_(CMAX,c) evenly among the number ofPUCCH transmissions (e.g., n PUCCH transmissions in a given subframe).For example, the uplink power of each PUCCH transmission may be set to amaximum of P_(CMAX,c)/n, where n may be the number of PUCCHtransmissions in the subframe.

In an example, each MAC instance/serving site may be configured with aMAC-specific maximum output power. For example, the value P_(CMAX,c,i)may represent the maximum transmit power for MAC instance i and/orserving site i. The PUCCH transmission ins serving site i may beallocated P_(CMAX,c,i). The values of P_(CMAX,c,i) may be different fordifferent MAC instances/serving site (e.g., values of i).

In an example, the WTRU may be provided with a WTRU-specific value forP_(CMAX,c) and a priority list and/or indication for PUCCHtransmissions. The transmit power for the different PUCCH transmissionmay be allocated according to the priority list. For example, power maybe first allocated to the highest priority PUCCH transmission (e.g.,total requested power), then use the remaining power (e.g.,P_(CMAX,c)−P_(PUCCH,i), where P_(PUCCH,i) may represent the powerallocated to the highest priority PUUCH) as a new P_(CMAX,c) value andallocate power to the second highest priority PUCCH transmission, and soon. In this example, if the WTRU allocates the total request power tothe higher priority PUCCH transmission, the WTRU may have insufficientpower to be able to transmit one or more PUCCH transmissions to lowerpriority serving sites.

In an example, the WTRU may allocate power to different PUCCHtransmissions independently. For example, after allocating transmissionpower to each of the PUCCHs to be sent in a given subframe, if the sumof the transmission powers exceed the maximum transmit power (e.g.,P_(CMAX,c)), the WTRU may scale the transmission in order to avoidexceeding its maximum transmit power.

If the different MAC instances/serving sites are associated withdifferent component carriers, the total transmission power summed overeach of the carriers may be fixed. For example, each carrier may have anindependent value of P_(CMAX,c), which for example may be set based onpriority rules for transmission of PUCCH on each carrier. If a PUCCHtransmission is not performed on one or more of the component carriersand/or if the power allocated for a PUCCH transmission on a componentcarrier is less than the corresponding value of P_(CMAX,c) for thatcarrier, then the value of P_(CMAX,c) for that component carrier may bedecreased by a preconfigured amount. The unused power and/or the amountof the decrease may be reallocated to other carriers to use for PUCCHtransmissions.

In an example, the actual power used by each of the PUCCH transmissionsin a subframe may be summed and any remaining power may be used for oneor PUSCH transmissions to one or more of the serving sites. The powerused for PUSCH transmissions may be configured/allocated independentlyfor the different serving sites. Scaling of transmit power between thedifferent serving sites for a PUSCH transmission may depend on apre-configured priority rule. For example, the remaining power percarrier (P_(CMAX,c) if there is no PUCCH transmission andP_(CMAX,c)−P_(PUCCH) for simultaneous PUSCH-PUCCH transmission on thecarrier) may first be allocated to the highest priority PUSCH. Anyremaining power may then be allocated to the next highest priorityPUSCH, and so on. Similar priority based rules may be used for PUSCHtransmission as are described with respect to PUCCH transmission. Forexample, the configuration of priority rules for PUSCH transmission maybe implicitly determined based on the priority rules applied for PUCCHtransmission (or vice versa).

In order for a WTRU to receive multiple DL transmissions on the samecarrier (or on different carriers), the WTRU may be configured with timesegregation or frequency segregation for DL transmissions in a mannersimilar to that as described for UL transmission. For example, a servingsite/cell may indicate to the WTRU the amount of traffic it has bufferedfor that WTRU. The WTRU may obtain such the buffer metrics for eachserving site. The WTRU may use the metric to determine ratio ofresources (e.g., time resources, frequency resources, etc.) to beallocated for each serving site. The WTRU may request the appropriateamount of resources from each sites. If there was a previous allocationof resources that is still active, the WTRU may request modification ofresources (e.g., fewer subframes assigned to a first serving site and/ora larger number of subframes assigned to a second serving site; fewer BWparts assigned to a first serving site and/or a larger BW parts ofsubframes assigned to a second serving site; etc.).

A WTRU may be configured with a different C-RNTI for each serving site.The WTRU may detect and attempt to decode PDCCH transmissions scrambledwith any of its assigned C-RNTIs. The C-RNTI used may indicate to theWTRU which serving site/MAC instance is associated with the DLtransmission (e.g., a PDCCH transmission of a first site being decodedwith a C-RNTI associated with a second serving site may indicate thatthe PDSCH transmission/PUSCH transmission allocated by the PDCCHtransmission is to sent/received on the second serving site). The C-RNTIused to decode a DL transmission (e.g., PDCCH transmission, PUSCHtransmission, etc.) may indicate the resources/serving site to be usedfor UL feedback for the DL transmission.

A PDCCH may be segregated in time and/or frequency. For example, iffrequency segregation is used, a serving site may segregate one or morespecific control channel elements (CCEs), for example CCEs included inWTRU-specific BW parts, to WTRUs who may be configured with frequencysegregation. Such frequency segregation may affect the search-space tobe used by a transmission point for a given WTRU.

A serving site may configure the WTRU to monitor unique ePDCCHresources. For example, each ePDCCH may use different resources (e.g.,different RB(s) and/or different subframe configurations, etc.). Theresources used for ePDCCH may indicate to the WTRU the appropriateresources to use in UL for that site. For example, there may be animplicit mapping between the DL resources used for ePDCCH transmissionand the UL resources to be used for transmitting over to a given servingsite.

Time segregation in the downlink may be implemented in a manner similarto enhance inter-cell interference coordination (eICIC). For example,the WTRU may determine contents and/or type of feedback to transmit at agiven feedback instance (and/or one or more serving site-specificparameters to use for such feedback) based on the identity of thesubframe during which an aperiodic feedback is triggered. For example,if feedback is triggered in a subframe that is not included in the TDMconfiguration for the serving site, the WTRU may wait until the nextavailable subframe that is associated with the relevant site in order totransmit the feedback (e.g., aperiodic CSI feedback).

A WTRU may perform random access procedure on one or more (and/or any)of the serving sites/cells associated with the serving sites. Forexample, when establishing an initial radio link to a serving site, aWTRU may have already established a radio link to another serving siteon the same carrier or a different carrier. For example, the WTRU mayalready have an established RRC connection to another site (e.g., to aMeNB). The WTRU may inform the serving site that it is attempting toaccess (e.g., a SCeNB) that the WTRU has a radio link to another servingsite (and/or multiple other serving sites). For example, the WTRU mayinclude an indication in a message exchanged in the random accessprocedure (e.g., such as in message 3) that indicates that the WTRU hasa previously established connection to a different serving site. Theserving site that the WTRU is attempting to access via RACH may providededicated PRACH resources and/or dedicated PRACH preambles for WTRUsthat have established connections to other serving sites.

In an example, an RRC message similar to a handover command may bereceived from a first serving site to which the WTRU is alreadyconnected, and the message may trigger the WTRU to perform an initialaccess procedure to a second serving site. For example, the RRC messagemay include dedicated PRACH resources and/or a dedicated preamble to beused for the RACH on the PRACH resources of the second serving site. Thesubbands (and/or BW part) within which a WTRU mat attempt RACH mayimplicitly indicate whether or not the WTRU has an established radiolink to another serving site (e.g., if RACH is performed in a first BWpart the WTRU may have an established connection to a different servingsite, if the WTRU attempts RACH in a second BW part the WTRU may lack aconnection to another serving site). The PRACH resource used for thetransmission of a preamble may indicate whether or not it has a radiolink to another site. For example, certain dedicated RAC preamblesand/or certain PRACH resources may be reserved for access attemptsperformed by WTRUs with an established connection to a different servingsite. The WTRU may indicate whether the RACH is for the establishment ofa secondary RRC connection or a primary RRC connection.

When attempting random access to a serving site, the WTRU may report aset of IDs (e.g., MAC instance IDs, serving cite ID, cell IDs, etc.) toindicate the set of one or more serving sites with which the WTRU mayhave a radio link. This may allow the new serving site to begin aprocedure to establish a backhaul connection to other serving site(s)utilized by the WTRU (e.g., via X2, X2bis, and/or any other interface).A WTRU may indicate the ratio of resources it would like from theserving site (e.g., a subframe density or ratio for TDM operation, etc.)during the random access procedure. For example, the indication may beincluded in RACH messages when the WTRU sends a scheduling request to asecond serving site for UL traffic. For example, the WTRU may betransmitting UL traffic to a first serving site and based on the desiredQoS (e.g., of one or more transmissions) the WTRU may request ratio ofresources to be utilized between the first serving site and the secondserving site.

A WTRU may concurrently transmit UL channels to multiple serving sitesby using different orthogonal cover codes (OCCs) for each of the servingsites. For example, a WTRU may be configured for transmitting PUCCH tomultiple serving sites (e.g., a first PUCCH to a first serving site, asecond PUCCH to a second serving site, etc.). The WTRU may be configuredwith one or more serving site (and/or MAC instance) specific OCCs. TheOCC to be used for a given serving site may be a function of a cell ID(and/or virtual cell ID) associated with a serving site, a C-RNTIassociated with the serving site, a serving site ID associated with theserving site, a MAC instance ID associated with the serving site, and/orthe like.

The configuration of the OCC to be used at a given serving site may beperformed in a manner similar to those described with respect toconfiguring subframe subsets for a serving site (e.g., time segregation)and/or BW parts of the serving site (e.g., frequency segregation). Codesegregation for a given serving site may be performed in addition totime segregation and/or frequency segregation. A WTRU may be configuredwith an OCC to be used for PUCCH transmissions. The OCC may be indicatedin the initial PUCCH configuration for the serving site. The OCC to beused for a PUCCH transmission may depend on the type of PUCCH formatused for the PUCCH transmission. In an example, the OCC to be used forPUCCH for transmitting HARQ feedback may be assigned based on the DCIused for downlink assignment. For example, the OCC to be used may beimplicitly mapped to the number of the first CCE that included the CDI.In an example, the OCC may be obtained as a function of the cell ID(and/or virtual cell ID) of a cell of the serving site and/or aWTRU-specific parameter or ID.

As shown in FIG. 2, a variety of priority rules may be used to selectbetween MAC instances in cases of contention of resources. For example,a plurality of priority rules may be used to determine the appropriateserving site to use for a transmission. The priority rules may betiered. For example, if two serving sites/MAC instances have a samepriority level for a first priority tier, then a second priority tiermay be considered for determining with MAC instance should be grantedthe physical resources. Multiple priority rules can be used to determinepriority between MAC instances. An order of precedence may be definedbetween different priority rules.

As shown in FIG. 2, the priority level of a given serving site/MACinstance may be determined based on one or more of the type of physicalchannel (202), the type of MAC instance (206), the type of informationto be transmitted (208), the logical channel priority (210), theMAC-specific aggregated QoS configuration (212), the identity of anongoing procedure (214), a radio link condition (216), a duration sincethe last transmission (218), a measured pathloss (220), a received grant(222), a radio link condition (224), and/or other factors. The variousfactors used to determine the priority may be tiered, and some factorsmay be the primary factors used to determine a priority while otherfactors may be used for a secondary priority (and/or third, fourth,fifth levels of priority and so on).

In an example, a priority level for transmitting using a given MACinstance/serving site may be determined based on a type of physicalchannel to be used for transmission by the MAC instance. For example, afirst MAC instance transmitting PUSCH to a first serving site may havehigher priority than a second MAC instance transmitting PUCCH to asecond serving site (or vice versa).

In an example, a priority level for transmitting using a given MACinstance/serving site may be determined based on a type of the MACinstance/serving site. For example, the priority rule may be definedbased on the serving site associated with the MAC instance (e.g.,whether the serving site corresponds to a MeNB or a SCeNB). For example,a transmission to a MeNB may be prioritized over a transmission to anSCeNB (or vice versa). In an example, a serving site that serves as amobility anchor for the WTRU may be prioritized over a serving site thatis not a mobility anchor. The configuration of the MAC instance mayinclude an index that corresponds to a priority level for that MACinstance. In an example, a primary MAC instance may be prioritized overa secondary MAC instance.

In an example, a priority level for transmitting using a given MACinstance/serving site may be determined based on a type of theinformation that is to be transmitted. For example, a priority ruledefined based on the type of information to be transmitted mayprioritize UCI and/or a certain type of UCI (e.g., HARQ A/N, SR,periodic or aperiodic CSI, etc.) over user data. Certain types of UCImay be prioritized over other types of UCI. For example, a MAC instanceattempting to transmit HARQ A/N may have a higher priority than a MACinstance attempting to transmit CSI and/or a MAC instance attempting totransmit user data. In another example, a MAC instance that isdynamically scheduled for PUSCH transmission may have higher prioritythan a MAC instance that is not scheduled for PUSCH transmission. In anexample, a MAC instance for which an adaptive or non-adaptiveretransmission is scheduled may have higher priority than a MAC instancefor which a new transmission is scheduled. In an example, a firstmessage type (e.g., an RRC request and/or an RRC response message) maybe given higher priority than other types of messages.

In an example, a priority level for transmitting using a given MACinstance/serving site may be determined based on the logical channelpriority of the logical channel to be transmitted using a given MACinstance. For example, the MAC instance attempting to transmit data forthe higher priority logical channel may be given priority over a MACinstance attempting to transmit data for a lower priority logicalchannel. In an example, the QoS of the corresponding radio bearerassociated with a MAC instance may be used to determine the relativepriority of the MAC instance. For example, a MAC instance being used totransmit data of a radio bearer with more stringent QoS requirements maybe prioritized over a MAC instance being used to transmit data of aradio bearer with less stringent QoS requirements. In an example, apriority level for transmitting using a given MAC instance/serving sitemay be determined based on the prioritized bit rate (PBR) of the logicalchannel associated with a MAC instance. For example, the WTRU mayprioritize a MAC instance being used to transmit a logical channel whosePBR has not been met over a MAC instance being used to transmit alogical channel whose PBR has been met. For example, a transmission maybe allocated for a logical channel of a MAC instance whose PBR has beensatisfied if the PBR of the other logical channels of other MACinstance(s) have been met. If there is a logical channel whose PBR hasnot been met, the MAC instance transmitting that logical channel may beprioritized.

In an example, a priority level for transmitting using a given MACinstance/serving site may be determined based on MAC-specific aggregatedQoS configuration. For example, a WRTU may be configured with a set ofone or more QoS parameters for a given MAC instance. In an example, theWTRU may determine the set of one or more QoS parameters for a given MACinstance as a function of the configuration of the individual logicalchannels (LCHs) and/or logical channel groups (LCGs) for the MACinstance. Examples of QoS parameters may include one or more of a PBR(e.g., such as a PBR value aggregated across a plurality of LCHs/LCGs ofthe concerned MAC instance), a minimum latency value (e.g., such as themost stringent discard timer value across a plurality of LCHs/LCGs ofthe concerned MAC instance and/or a threshold for the maximum head ofqueue delay and/or the smallest value of the discard timer for a givenSDU in the WTRU buffer), a priority threshold (e.g., such that the WTRUmay determine the MAC-specific QoS parameters taking into accountLCHs/LCGs of a priority equal to or above the threshold), and/or thelike.

In an example, a priority level for transmitting using a given MACinstance/serving site may be determined based on the identity of anongoing procedure associated with a MAC instance/serving site. Forexample, a WTRU may initiate a procedure such as a RRC procedure thatmay have higher priority than other procedures such as the transmissionof data (e.g., transfer of user plane data). Examples of procedures thatmay be prioritized over dynamically scheduled data transfers may includeone or more of a semi-persistent transmission, the transmission orretransmission of a bundle, a preamble transmission in a RACH procedure,another type of transmission in a RACH procedure, an RRC procedure(e.g., transmission of a measurement report, a reconfiguration withmobility procedure, and/or the like) a procedure related to connectivitymanagement, etc. When the WTRU initiates a procedure that is of higherpriority than dynamically scheduled user data transmissions, the WTRUmay prioritize transmission for a MAC instance that corresponds to theprioritized procedure such that the MAC instance is allocated more powerin case of contention for the allocation of power with othertransmission(s) of the WTRU.

In an example, a priority level for transmitting using a given MACinstance/serving site may be determined based on radio link conditions.For example, a WTRU may determine that the radio link condition may bebelow a given threshold for transmissions associated with a given MACinstance. For example, the WTRU may detect radio link problems as partof a radio link monitoring procedure. The WTRU may prioritize a MACinstance experiencing stronger radio link conditions or a MAC instanceassociated with poorer radio link conditions. In an example, the WTRUmay prioritize a MAC instance based on a determined pathloss for theserving site associated with the MAC instance. For example, if thepathloss associated with a given MAC instance exceeds a given threshold,the WTRU may determine to prioritize other MAC instances that areassociated with a lower pathloss. In an example, the WTRU may determinethat one or more cells associated with a given MAC instance isexperiencing radio link failure (RLF). The WTRU may prioritize MACinstances that are associated with cells that are not experience RLFover cells that are experiencing RLF. In an example, one or more of ULRLF and/or DL RLF may be considered. In an example, the WTRU maydetermine that RRC timer T310 is running for a given MAC instance. TheWTRU may prioritize a MAC instance whose T310 timer is not running overa MAC instance whose T310 timer is running.

In an example, if a given MAC instance is not used for connectivity(e.g., a MAC instance that is not the primary MAC instance and/or is notused for transmitting RRC messages), the WTRU may associate a specific(e.g., possibly lower and/or absolute lowest) priority to transmissionsfor the concerned MAC instance. For example, ifs first MAC instance isused for connectivity (e.g., if the first MAC instance is the primaryMAC instance and/or is used for maintaining the RRC connection), theWTRU may associate a specific (e.g., possibly higher and/or absolutehighest) priority to transmission for that MAC instance. The WTRU mayassign a higher priority (and/or absolute highest priority) to a MACinstance whose RRC timer(s) T301, T302, T304 and/or T311 is/are running(e.g., which may indicate an ongoing procedure related to connectivity,mobility, and/or re-establishment is being performed).

In an example, a priority level for transmitting using a given MACinstance/serving site may be determined based on a time since a lasttransmission was performed for a given MAC instance. For example, apriority rule may be defined based on a duration since the last subframethat was available to the MAC instance and/or a duration since the lastsubframe that was actually used by the MAC instance for transmission.For example, a AMC instance associated with a longer duration may beassigned a higher relative priority than a MAC instance with a shorterduration.

In an example, a priority level for transmitting using a given MACinstance/serving site may be determined based on a determined pathlossfor the MAC instance. For example, an estimated pathloss for a servingcell, such as a PCell, of a MAC instance may be determined by the WTRU.The WTRU may prioritize a MAC instance for which the pathloss is lowerover a MAC instance for which the pathloss is higher. As anotherexample, rather than or in addition to a determined pathloss, thepriority determination may be made based on one or more of an estimateddownlink channel quality, for example based on CSI and/or measuredreference signal received power (RSRP).

In an example, a priority level for transmitting using a given MACinstance/serving site may be determined based on the received grant ofthe MAC instance. For example, the priority rule may be defined based onthe absolute received grant and/or based on a grant to power ratio. Forinstance, a MAC instance for which a higher grant has been signaled mayhave higher priority. As another example, the priority rules may bebased on an estimated UL packet error rate for each MAC instance and/orbased on available headroom for a given MAC instance. For example, theMAC instance with the lower packet error rate and/or the MAC instancewith the highest power headroom may be given higher priority.

In an example, a priority level for transmitting using a given MACinstance/serving site may be determined based on past priorityenforcement. For example, the priority of a serving site and/or physicalchannel of a serving site may change based on whether a previoustransmission for the serving site was dropped based on the transmissionhaving a lower priority than a transmission of another MAC instance. Forexample, if a WTRU drops PUSCH to a first serving site based on a totransmission of PUCCH to a first serving site having priority, one ormore of a PUSCH transmission and/or a first serving site transmission(or the combination of the two) may be given a higher priority in thenext overlapping subframe. The new, heightened priority may beapplicable until the specific signal that was dropped has beentransmitted. For example, if a PUSCH transmission to a first servingsite was dropped based on the PUSCH transmission having a lower prioritythan another transmission associated with a different MAC instance, butin a future non-overlapping subframe the WTRU is able to transmit thisPUSCH to the first serving site (e.g., before it overlaps a second timewith the MAC instance that was prioritized over it), the priority rulemay revert back to the original configuration.

Various combinations of the priority rules may be used. For example, theWTRU may prioritize a transmission on a PUSCH associated with a servingcell of a prioritized MAC instance (e.g., a primary MAC) over atransmission on the PUCCH associated with a serving cell of a secondaryMAC that has a with lesser priority.

In an example, rather than or in addition to WTRU-autonomous priorityrules, the WTRU may receive one or more explicit indications from thenetwork (e.g., one or more serving sites) for selecting between MACinstances in case of contention. The network based priority indicationsmay be applicable to one or more of non-simultaneous and/or simultaneoususe of physical resources. The explicit indication of priority may bereceived via one or more of L1 signaling (e.g., PHY signaling such asthe PDCCH and/or E-PDCCH), L2 signaling (e.g., MAC), and/or L3 signaling(e.g., RRC).

For example, the WTRU may receive L1 signaling include DCI via one ormore of the PDCCH and/or E-PDCCH (e.g., for dynamic and/orsemi-persistently scheduled grants). The DCI may include a flag and/orother indication of a priority value that may be associated with thegrant included in the DCI. For example, the flag and/other indicationmay indicate that the grant will have a specific priority, for example apriority that is different that a default priority for a typical grantof the given type. The WTRU may use the indication of priority whenperforming logical channel prioritization such that data with acorresponding priority may be included in the MAC PDU that may betransmitted in the transport block that corresponds to the receivedgrant. In an example, the WTRU may receive DCI that triggers thetransmission of a preamble (e.g., a PDCCH order for random access and/orfor the purpose of proximity detection). The DCI may include a flagand/or other indication of a priority value for the preambletransmission (and/or possibly any WTRU-autonomous preambleretransmission for the concerned procedure). Flags or indications ofpriority in DCI may indicate that the grant is of higher priority than agrant that does not include the flag or indication. The WTRU mayimplicitly determine that such priority may be applied to the preambletransmission as a function of the indicated PRACH parameter (e.g.,preamble index, PRACH mask index, etc.) and or associated PRACH resource(e.g., in case partitioning or PRACH is configured).

In an example, the WTRU may receive DCI via L1 signaling that mayactivate a specific prioritization rule for the concerned MAC instance.For example, the activation of the priority rule may be time-limited,and an indication of the length of time the priority rule should be usedbe may also be signaled in the concerned DCI. For example, the DCI mayindicate that transmission associated with a first MAC instance may havehigher priority than transmissions for another MAC instance for aspecified period of time. The WTRU may transmit a HARQ feedbackacknowledgement when it receives such DCI. In another example, the DCImay trigger the WTRU to begin using (and/or stop using) one or more ofthe priority criteria described with respect to FIG. 2.

L2 signaling may be used to explicitly signal a priority for a given MACinstance. MAC CEs may be an example of L2 signaling. For example, theWTRU may receive a MAC CE that activates a specific prioritization rulefor the concerned MAC. For example, the activation of the priority rulemay be time-limited, and an indication of the length of time thepriority rule should be used be may also be signaled in the concernedMAC CE. For example, the MAC CE may indicate that transmissionassociated with a first MAC instance may have higher priority thantransmissions for another MAC instance for a specified period of time.In another example, the MAC CE may trigger the WTRU to begin using(and/or stop using) one or more of the priority criteria described withrespect to FIG. 2.

L3 signaling may be used to explicitly signal a priority for a given MACinstance. RRC PDUs may be an example of L3 signaling. For example, theWTRU may receive an RRC PDU that may initiate a procedure that mayactivate a specific prioritization rule for MAC associated withtransmissions of RRC PDUs (e.g., a SRB) corresponding to the concernedprocedure. An RRC PDU may include an explicit flag and/or a priorityvalue indicating that subsequent PDUs for this procedure shall have aspecific (e.g., higher) priority. When the WTRU initiates theprioritized procedure, the WTRU give priority to a MAC instance thatcorresponds to the concerned procedure (e.g., may be allocated morepower in case of contention for the allocation of power with othertransmission(s) of the WTRU and/or may be transmitted rather thandropped in the case of a conflict where time segregation is used). Anindication of priority included in an RRC PDU may include a flag thatindicates an alternative and/or an absolute priority rule, an index thatindicates a specific priority rule, and/or an offset or a weight valueto apply to the prioritization process.

Combinations of these priority rules, and possibly also withWTRU-autonomous methods described herein may be used. For example, theWTRU may be configured to implement autonomous priority rules but suchautonomous prioritization rules may be overridden by explicitly signalednetwork-controlled priority rules.

In an example, certain physical layer procedures may be different and/ormodified when a multi-site configuration is enabled as compared to whena single serving site is utilized. For example, a WTRU may receive aPhysical HARQ Indicator Channel (PHICH) from multiple sites when amulti-site configuration is enabled. The PHICHs of the different servingsites may be time-segregated, frequency-segregated, and/orcode-segregated. If PHICH is code-segregated per site, a WTRU mayindicate to each site a site index. In an example, the site index may beexchanged between sites via an interface such as the X2 interface. Thevalue of the site index may be used in determining the PHICH sequencenumber of the PHICH, thus ensuring that each site has an orthogonalPHICH. In an example, the sites may explicitly indicate to each othervia an interface such as the X2 interface the PHICH sequence number thatthe serving site is using, for example to ensure orthogonality of thePHICH of the different serving sites.

If frequency segregation of serving sites is utilized, each site may usea different PHICH group number. For example, the serving sites may beassociated with a WTRU-indicated site index to be used for determiningthe PHICH group number. In an example, the site index may be exchangedbetween the sites via an interface such as the X2 interface. In anexample, the PHICH group number may be explicitly exchanged betweensites to ensure that PHICH group numbers are not reused between servingsites.

If time segregation of serving sites is utilized, each site may includeone or more subframes of a subframe subset where PHICH may betransmitted. In order to ensure that each serving site has access toPHICH resources in subframe(n+k_(PHICH)) for a WTRU that transmittedPUSCH in subframe(n), the WTRU may be configure with a servingsite-specific value of k_(PHICH). In another example, the WTRU may beaware of the subframes in the subsets that may be used for PHICH foreach serving site. For example, when determining a subframe where a WTRUmay expect PHICH (e.g., subframe(n+k_(PHICH))), the WTRU may count validsubframes assigned to the concerned serving site (e.g., subframes withineach site's PHICH subframe set) when determining a appropriate number ofsubframes (e.g., k_(PHICH) subframes) has elapsed.

In an example, the value of k_(PHICH) used for a given serving site maydepend on the identity of subframe(n) in which the WTRU transmitted onthe PUSCH. For example, a set of values for k_(PHICH) may bepre-configured. The WTRU may select a value that will result in PHICHbeing transmitted in a valid subframe for the serving site. For example,the set of k_(PHICH) per subframe(n) may be jointly configured with asubframe set of valid PUSCH subframes to a given site.

In an example, HARQ-ACK bundling may be used on PHICH. For example, thenetwork may bundle a plurality of HARQ-ACK indications onto single PHICHtransmission occurring at subframe(n+k_(PHICH)). The PHICH may includeHARQ ACK/NACK indication for each PUSCH transmission occurring insubframe(n) or earlier that has not yet been ACKed/NACKed. For example,an indicator bitmap may be transmitted by the network to indicate howmany PUSCH transmissions the HARQ-ACK bundle is for (e.g., one bit foreach PUSCH transmission). In an example, multiplexing of HARQ-ACK may beused. For example, a given serving site may accumulate HARQ-ACK until aconfigured subframe(m) in its PHICH subframe set occurs. Upon reachingthe configured subframe, each of the HARQ-ACK/NACKs for PUSCHtransmissions from subframe(m-k_(PHICH)) or earlier that have not yetbeen ACK/NACKed may be transmitted. Each HARQ-ACK may use a differentorthogonal code, for example as determined by the PHICH sequence number.In such a case, each PUSCH transmission may be given an index and theindex may be used in the PHICH sequence number formulation.

In an example, the WTRU may be configured to operate using multiple setsof transmission parameters and may select one or more appropriate set(s)of transmission parameters to use in a given subframe based on variouscriteria. For example, if a given subframe is to be used by the WTRU inorder to perform a plurality of uplink transmissions (e.g.,transmissions to different serving sites), the WTRU may determine a setof transmission parameters to use for one or more PUSCH transmissionsbased on criteria such as the transmission requirements across aplurality of layers/serving sites. As an example, the transmission powerrequested and/or configured for each transmissions site may beconsidered by the WTRU when selecting appropriate transmissionparameters to apply for transmissions sent to one or more of the servingsites. The sets of transmission parameters that may be used by the WTRUmay be obtained by the WTRU in a number of ways. For example, the WTRUmay receive one or more parameters (e.g., and/or one or more sets ofparameters) via downlink control signaling such as a PDCCH transmission.In an example, the WTRU may receive one or more parameters (e.g., and/orone or more sets of parameters) as a semi-static configuration (e.g.,for a configured grant such as a semi-persistent scheduling (SPS) grant,a configuration of alternate parameters, an RRC configuration ofparameters, etc.). In an example, the WTRU may implicitly determine oneor more parameters (e.g., and/or one or more sets of parameters). Forexample, the WTRU may implicitly determine one or more one or moreparameters (e.g., and/or one or more sets of parameters) for a firstlayer/serving site based on one or more parameters (e.g., and/or one ormore sets of parameters) that are applied at a second layer/servingsite.

For example, the WTRU may determine one or more transmission parametersto be applied for a given uplink grant in a first layer (e.g.,associated with a first serving site and/or a first MAC instance) basedon the parameters applied to an uplink transmission in a second layer(e.g., associated with a second serving site and/or a second MACinstance). For example, for a subframe during whichconcurrent/simultaneous UL transmission is to be performed for more thanone MAC instance/layer, the WTRU may be configured to select one or moretransmission parameters to use for a PUSCH transmission in a first layerassociated with a first serving site (e.g., and/or MAC instance) basedon the existence of a transmission in a second layer associated with afirst serving site (e.g., the parameters used in the first layer maychange depending on whether or not a transmission in a second layer isto occur concurrently) and/or based on one more characteristics of ULtransmission on the second layer. For example, one or more of amodulation and coding scheme (MCS), a redundancy version, a total numberof allocated PRBs, a number of coded symbols for control information,and/or the transport block size used for transmission in a first layerassociated with a first serving site may be selected based on whether ornot transmission is to be sent to a second serving site concurrently. Inan example, one or more of an MCS, a redundancy version, a total numberof allocated PRBs, a number of coded symbols for control information,and/or the transport block size used for transmission in a first layerassociated with a first serving site may be selected based the identityof one or more uplink transmission parameters to be used for concurrenttransmission to a second serving site (e.g., an MCS, a redundancyversion, a total number of allocated PRBs, a number of coded symbols forcontrol information, and/or the transport block size used fortransmission to the second serving site).

Transmission parameters for use for transmission(s) sent to firstserving site may be selected based on parameters related totransmissions to a second serving site in order to maintainpredictability of block error rate performance, for example when theavailable transmission power for a given serving site is uncertain dueto potential transmissions to other serving sites. Examples of differentcriteria the WTRU may use to select transmission parameters to beapplied for transmissions to be sent to a first serving site based onone or more parameters associated with uplink transmissions for a secondserving site are described in more detail below.

For example, the WTRU may select a first set of transmission parametersfor PUSCH transmitted in a first layer associated with a first servingsite as a function of whether or not the WTRU is to perform multi-layertransmission (e.g., concurrent transmission to multiple serving sites inthe same subframe) in a given subframe. The WTRU may select a first setof one or more uplink transmission parameters to apply for transmissionto a first serving site if the WTRU is not transmitting to a secondserving site in the same subframe as the transmission to the firstserving site and/or the WTRU may select a second set of one or moreuplink transmission parameters to apply for transmission to the firstserving site if the WTRU is transmitting to the second serving site inthe same subframe as the transmission to the first serving site.

In an example, the WTRU may determine the transmission parameters toapply for transmission to a given serving sites based on DCI contentsreceived for one or more of the serving sites. As an example, the WTRUmay receive DCI applicable to a PUSCH transmission to a given servingsite for one or more subframes (e.g., a dynamic grant on PDCCH, an SPSconfiguration, an SPS activation message, etc.). The DCI may indicatemultiple values for one or more transmission parameters (e.g., an MCS, aredundancy version, a total number of allocated PRBs, a number of codedsymbols for control information, a transport block size, etc.), and theWTRU may select which of the values should be applied based on whetherthe WTRU is concurrently transmitting to another serving site in thesame subframe as the PUSCH transmission. For example, a received grantmay include two values for the MCS, where one MCS value is applicable totransmissions where the WTRU is not performing concurrent transmissionsto multiple serving sites in the same subframe and a second isapplicable to transmissions where the WTRU is performing concurrenttransmission to multiple serving sites in the same subframe.

In an example, the WTRU may determine the transmission parameters toapply for transmission to a given serving site based on the identity ofone or more transmission parameters applied for transmission to anotherserving site. For example, the WTRU may be preconfigured and/or receiveRRC signaling that configures one or more parameters that the WTRUshould apply for transmissions to a second serving site based on theparameters/configurations applied to a first serving site. As anexample, the second set of parameters to be used for a transmission to asecond serving site may be determined and/or derived from a first set ofparameters that are indicated in DCI for a first serving site. The WTRUmay have a predefined configuration and/or may receive a configurationvia higher layer signaling that indicates which parameters are used fortransmission to a second serving site when certain other parameters arebeing used for a concurrent transmission to a first serving site in thesame subframe. As an example, an MCS index to use for the second set ofparameters (e.g., for a transmission to a first serving site) may bedetermined function of an MCS indicated to be used for transmission tothe first serving site (e.g., in DCI). The MCS index (and/or othertransmission parameter) to use for transmission to the second servingsite may be selected based on the MCS index associated with thetransmission to the first serving site and an offset value. For example,the MCS index of the second serving site may be selected as the MCSvalue of the first serving site minus the offset value (e.g., subject toa minimum). The offset value may be predefined, received from higherlayer (e.g., RRC) signaling and/or indicated in DCI. As another example,the total number of allocated PRBs for transmission to the secondserving site (and/or some other parameter of the second set of uplinktransmission parameters) may be determined to be the number of PRBsallocated for transmission to the first serving set reduced by apredetermine number or factor (e.g., rounded up or down to a validnumber of allocated PRBs).

In an example, the WTRU may determine the transmission parameters toapply for transmission to a given serving site based on the identity ofone or more transmission parameters applied for transmission to anotherserving site and the available transmit power for the subframe. Forexample, a second set of one or more transmission parameters to beapplied to a transmission to a second serving site may be determinedand/or derived based on a first set of one or more transmissionparameters to be applied in a transmission to a first serving site(e.g., as indicated in a received DCI) and one or more of thetransmission power to be applied in the first layer if transmission inthe second layer occurs in the same subframe and/or the transmissionpower to be applied in the first layer in the absence of transmission inthe second layer in the same subframe. As an example, the MCS indexand/or the number of allocated PRBs (and/or some other uplinktransmission parameter) of a second set of parameters to be applied totransmission to a second serving site may be determined and/or derivedbased on the corresponding parameter applied for the first set ofparameters used for transmission to the first serving site (e.g., MCSindex, number of allocated PRBs, etc.) and a ratio of the availabletransmission power if a transmission is sent to a single serving site(e.g., the first serving site) in a given subframe and the availabletransmission power if a transmission is sent to multiple serving sites(e.g., the first serving site and the second serving site) in thesubframe. For example, a function of the ratio of the availabletransmission powers with no transmission in a second layer in a givensubframe to the available transmission power with transmission in thesecond layer in the subframe may be used to scale a parameter associatedwith transmission to the first serving site for use transmitting thesecond serving site. As an example, a second set of one or moretransmission parameters to be applied to a transmission to a secondserving site may be determined and/or derived based on a first set ofone or more transmission parameters to be applied in a transmission to afirst serving site (e.g., as indicated in a received DCI) and theavailable transmission power if the second serving site is determined toof higher priority than the first serving site.

In an example, the WTRU may determine the transmission parameters toapply for transmission to a given serving site based on a second set ofDCI that is received for the subframe. For example, first DCI may bereceived and may define a set of transmission parameters to be appliedfor transmitting to the first serving site, and second DCI may bereceived and may define a set of transmission parameters to be appliedfor transmitting to the second serving site. The DCI for the firstserving site may be received via a PDCCH and/or E-PDCCH transmissionfrom the first serving site, and the DCI for the second serving site maybe received via a PDCCH and/or E-PDCCH transmission from the secondserving site. In another example, the DCI for both serving sites may bereceived from one of the serving sites. In a subframe during which theWTRU successfully decodes a plurality of DCI messages indicating anuplink grant for the same PUSCH, the WTRU may select which set ofparameters (e.g., which DCI) to use for the uplink transmission as afunction of the grant that would maximize the transmission of data andthe use of the WTRU's transmission power. In an example, the WTRU mayselect which set of parameters (e.g., which DCI) to use for the uplinktransmission as a function of the grant that would maximize thetransmission of data and the use of the WTRU's transmission power whileminimizing (and/or avoiding) the application of power reduction and/orpower scaling for the allocated PUSCH transmissions.

One or more sets of transmission parameters to be applied during periodsof concurrent transmission to different serving sites in the samesubframe may be applicable for a predetermined period of time and/orbounded in time. The WTRU may determine when to start and/or stopderiving a second set of transmission parameters for a given MACinstance or for a specific PUSCH according various criteria. Forexample, the WTRU may determine whether or not to utilize separatetransmission parameters for transmissions to different serving sitesand/or for how long the separate parameters should be used based onexplicit signaling. The WTRU may receive control signaling thatindicates to the WTRU that the WTRU should determine separate sets oftransmission parameters for the serving cells of different servingsites. The explicit signaling may indicate for how long the WTRU shouldcontinue to derive separate sets of parameters (e.g., a specific numberof subframes; until explicit signaling indicates that separateparameters should no longer be used, etc.) and/or may explicitlyindicate the second set of parameters. The explicit control signalingthat indicates that separate sets of transmission parameters should beused may be received by Layer 3 (e.g., RRC) signaling, for example aspart of a procedure that adds and/or modifies a given MAC instance. Inan example, explicit control signaling that indicates that separate setsof transmission parameters should be used may be received by Layer 2(e.g., MAC CE) signaling, for example as part of an indication for theconcerned MAC instance or for one or more of the serving cells of theMAC instance. In an example, explicit control signaling that indicatesthat separate sets of transmission parameters should be used may bereceived by Layer 1 DCI, for example in DCI that activates a second MACinstance/second set of transmission parameters. The WTRU may transmitHARQ feedback for the Layer 1 DCI. Explicit signaling (e.g., via Layer1, Layer 2, and/or Layer 3) may be used to indicate to the WTRU that itshould stop determining separate transmission parameters to be appliedfor different MAC instances.

The WTRU may determine when to begin and/or stop determining and/orutilizing a second, separate set of transmission parameters for a givenMAC instance and/or for a specific PUSCH based on the activation of MACinstance and/or the deactivation of a MAC instance. For example, theWTRU may be triggered to begin determining a separate set oftransmission parameters for a given MAC instance based on the activationof the given MAC instance and/or the activation of a different MACinstance. The WTRU may be triggered to stop determining a separate setof transmission parameters for a given MAC instance based on thedeactivation of the given MAC instance and/or the deactivation of adifferent MAC instance.

The WTRU may determine when to begin and/or stop determining and/orutilizing a second, separate set of transmission parameters for a givenMAC instance and/or for a specific PUSCH based on whether power scalingis to be applied in a given transmission. For example, the WTRU maydetermine to use and/or derive a second set of transmission parametersto use for a given MAC instance and/or PUSCH upon determining that powerscaling may be required in order to transmit to a second serving site ifa first set of transmission parameters are used for transmitting to afirst serving site. The determination regarding whether the second setof parameters should be derived and/or used for a given transmission maybe determined on a per subframe basis. In an example, the WTRU maydetermine to begin determining and/or deriving the second set oftransmission parameters based on having applied power scaling for apredetermined (e.g., a preconfigured and/or higher layer configured)number of subframes, a predetermined (e.g., a preconfigured and/orhigher layer configured) number of transmission, and/or forpredetermined (e.g., a preconfigured and/or higher layer configured)period of time. The WTRU may determine to begin determining and/orderiving the second set of transmission parameters based a correspondingPHR being triggered and/or transmitted. Similarly, the WTRU maydetermine when to stop determining and/or utilizing a second, separateset of transmission parameters for a given MAC instance and/or for aspecific PUSCH based on a determination that power scaling would nolonger be needed if the first (e.g., single) set of transmissionparameters would be used.

The WTRU may determine when to begin and/or stop determining and/orutilizing a second, separate set of transmission parameters for a givenMAC instance and/or for a specific PUSCH based on the QoS not being metin a given MAC layer/instance. For example, the WTRU may determine touse and/or derive a second set of transmission parameters to use for agiven MAC instance and/or PUSCH upon determining that one or more QoSrequirement(s) are not being met for one or more LCH of mapped to a MACinstance. The determination of whether to utilize separate transmissionparameters for different MAC instances based on QoS requirements may beperformed on a per subframe basis, on a scheduling period basis (e.g.,once per scheduling period), and/or after the QoS requirement has notmet for a predetermined and/or configurable period of time. The WTRU maydetermine to begin determining and/or deriving the second set oftransmission parameters in the subframe in which a corresponding QSR istriggered and/or transmitted. Similarly, t the WTRU may determine whento stop determining and/or utilizing a second, separate set oftransmission parameters for a given MAC instance and/or for a specificPUSCH based on the corresponding QoS requirement once again being met.

The WTRU may determine when to begin and/or stop determining and/orutilizing a second, separate set of transmission parameters for a givenMAC instance and/or for a specific PUSCH based on the expiration of atimer. For example, the WTRU may set a timer upon beginning to use asecond, separate set of transmission parameters for a given MAC instanceand/or for a specific PUSCH (e.g., based on receiving explicit signalingto use separate parameters and/or implicitly determining to start usingimplicit parameters). The WTRU may determine to stop determining and/orutilizing a second, separate set of transmission parameters for a givenMAC instance and/or for a specific PUSCH based on expiration of thetimer. The WTRU may restart the timer based on meeting one or more ofthe criteria described herein for triggering the WTRU to begin derivingthe separate transmission parameters (e.g., receiving explicitsignaling, activation of a MAC instance, application of power scaling,QoS not being met, etc.). The WTRU may stop using the second set oftransmission parameters when the timer expires.

The WTRU may be configured to indicate the set of transmissionparameters used for a PUSCH transmission in the PUSCH transmission. Forexample, the WTRU may be configured to multiplex UCI with the PUSCH databeing transmitted, and the UCI may indicate one or more of thetransmission parameters that were used by the WTRU to send the PUSCHtransmission. For example, in a PUSCH transmission where the WTRU mayselect between two or more sets of PUSCH transmission parameters, theWTRU may indicate which set of parameters has been selected and/or whichvalues were used for certain parameters. The selection may be encodedand multiplexed as UCI with UL-SCH data into the PUSCH transmission inpredetermined resource elements. For example, one bit may be reserved inthe PUSCH transmission for representing the selected set of transmissionparameters, for example if there are two sets of transmission parametersthe WTRU may select from (e.g., a 0 may indicate that the transmissionparameters utilized are that same for multiple MAC instances and/or a 1may indicate that different sets of transmission parameters are used fordifferent MAC instances). The indication regarding which transmissionparameter(s) are used may be appended to HARQ-ACK bits sent on the PUSCHand/or may be encoded in manner similar to HARQ-ACK bits sent on thePUSCH.

PDSCH procedures applied by the WTRU may depend on whether the WTRU isperforming multi-serving site transmission (e.g., in the uplink) and/orreception (e.g., in the downlink). For example, a WTRU may be configuredwith one or more pattern for performing UL transmission for each MACinstance (e.g., time segregation, frequency segregation, codesegregation, etc.). For DL reception (e.g., via the PDSCH), thedifferent serving sites (e.g., a first eNB such as a MeNB for the firstserving site and a second eNB such as an SCeNB for the second servingsite) may determine a DL time segregation pattern to be used fortransmitting to the WTRU while ensuring the applicable QoS parametersfor the different bearers are met. For example, the different servingsites may configure and/or negotiate a time segregation pattern fortransmitting to the WTRU in the downlink using the X2 interface (e.g.,X2′ interface, X2bis interface, etc.). In an example for timesegregation, the UL subframe subsets utilized by the WTRU may beconfigured independently of one or more DL subframe subset that may beused by the different serving sites for transmitting to the WTRU.Independently configured UL and DL subframe subsets may be referred toas decoupled UL and DL time segregation. When decoupled UL and DL timesegregation is used, the subframe subset configured for use may bedetermined based on the applicable conditions of the corresponding linkwithout having to take into consideration the applicable link conditionsin the reverse link. In another example, the UL and DL subframe subsetsmay be coupled and/or otherwise configured together such that ULsubframe subsets are jointly configured with and/or mapped to DLsubframe subsets.

For a given configured subset of UL subframes and a given configuredsubtest of DL subframes associate with a MAC instance, HARQ feedback forPDSCH transmission received in subframe(n) may be transmitted insubframe(n+k). The value of k may be determined based on the subframeindex n and the configuration of the subset of subframes available forUL operation. For example, k may be set to a value that ensures thatsubframe (n+k) is a subframe that is in the configured subset ofsubframes available for transmission to the serving site thattransmitted the PDSCH transmission in subframe(n). In an example, thevalue of k may be determined to ensure that subframe(n+k) is availablefor UL transmission while still allowing for sufficient processing timeto be available for the decoding of the PDSCH transmission. For example,k may be set to the smallest value greater than or equal to apredetermined minimum HARQ latency k0 (e.g., k0 may be equal to 4subframes) such that subframe(n+k) is included in the subframe subsetthat is configured for UL transmission for the associated MAC instance.

As an example, a PDSCH for a MAC instance may be configured to bereceived in any subframe, while UL transmissions (e.g., including one ormore of PUSCH and/or PUCCH) may be configured to be transmitted in asubset of subframes. For example, the UL subframe subset for the MACinstance may correspond to even-numbered subframes (e.g., subframes 0,2, 4, 6, and 8 of a frame). In such scenarios, the HARQ feedback forPDSCH transmissions received in subframes 0, 2, 4, 6 and 8 may betransmitted four subframes later (e.g. in subframes 4, 6, and 8 of thecurrent frame, and subframes 0 and 2 of the next frame, respectively),HARQ feedback for PDSCH transmissions received in subframes 1, 3, 5, 7,and 9 may be transmitted in five subframes later (e.g., the minimumnumber of subframes that is greater than the HARQ processing time offour subframes that still ensures the HARQ feedback is transmitted in asubframe in the UL subset for the MAC instance). For example, for PDSCHtransmissions received in subframes, 1, 3, 5, 7, and 9, the HARQfeedback may be transmitted in subframes 6 and 8 of the current frameand subframes 0, 2, and 4 of the next frame, respectively.

In an example, coupled UL/DL time segregation may be performed in orderto ensure the proper operation of HARQ. For example, a DL subframepattern that allows for DL transmission from a serving site to a WTRU insubframes a, b, c, and d, may be tied or otherwise mapped to a ULsubframe pattern that allows for UL transmission by the WTRU to the sameserving site in subframes a+4, b+4, c+4, and d+4. In this manner,previous release FDD HARQ rules may be applied while still allowing forsegregation of transmission to different serving sites.

In an example, the WTRU may be configured to treat each of the UL and/orDL subframe subsets as a block of “virtually continuous” subframes. Forexample, in this manner the legacy HARQ timing relationships may bemaintained across “virtually continuous” subframes even though theactual subframe subsets may be non-contiguous. For example, if a givenMAC instance is configured with a subset of subframes that includesubframe numbers 0, 1, 2, 3, 4, and 5 for both UL and DL transmission inall radio frames, the WTRU may apply the HARQ timing as if a frameincluded s subframes instead of 10 (e.g., the WTRU would treat subframe5 as if it was adjacent to subframe 0 for the next frame for thepurposes of HARQ transmission). As an example, HARQ timers and timingrelationships may be applied by the WTRU as if each virtual frameincluded the first six subframes of each actual radio frame. Forexample, if the WTRU receives a DL transmission in subframe #4 of afirst radio frame, the WTRU may transmit the corresponding UL HARQfeedback in virtual subframe(n+4), which may correspond to correspondingto subframe #2 of the following frame.

For some coupled and/or decoupled UL and DL time segregation, the UL andDL subframe subsets may be set such that reuse of FDD HARQ proceduresand timing may be infeasible. For example, if decoupled UL and DL timesegregation is utilized, the allocation of UL subframes may be muchdifferent that the allocation of DL subframes, HARQ operation usingprevious timing relationships unavailable.

As an example, consider a case where a WTRU is connected to two cells: afirst cell associated with a first serving site (e.g., Cell A) and asecond cell associated with a second serving site (e.g., Cell B). Cell Amay have buffered a relatively large amount downlink data to bedelivered to the WTRU. Therefore, the subframe subsets may be configuredsuch that 80% of the available DL subframes are included in the subframesubset associated with Cell A. Assuming a case where there is no overlapof subframe sets between different serving sites, the subframe subsetallocated for Cell B may include the remaining 20% of the available DLsubframes. However, in the uplink the WTRU may have a relatively largeamount of data buffered for transmission to Cell B, while having arelatively little amount of data buffered for transmission to Cell A. Insuch a case, Cell A may be allocated 20% of the UL subframes and Cell Bmay be allocated 80% of the UL subframes. As a result, Cell A maytransmit DL data to the in 80% of subframes, while the WTRU wouldtransmit in the UL to Cell A in 20% of subframes. The FDD HARQprocedures and timing (e.g., transmitting HARQ-ACK in subframe(n+k),where k=4 for DL data in subframe(n)) may be unworkable in such a case.

In an example, a WTRU may be configured to receive PDSCH from both MACinstances (e.g., receive PDSCH transmission from multiple serving sites)in each subframe, while UL transmissions for the corresponding MACinstances may occur in separate sets of subframes. For example, the WTRUmay be configured to transmit using a first MAC instance in subframes 0,1, 2, 3 and/or 4 of each frame and to transmit using a second MACinstance in subframes 5, 6, 7, 8, and/or 9 of each frame. If the PDSCHmay be received in any subframe but the uplink transmission path islimited to a subset of subframes, then the timing relationship betweenPDSCH and the transmission of corresponding HARQ-ACK may be defined in anumber of ways. For example, for the first MAC instance, HARQ-ACK forPDSCH received in subframes 1 and/or 2 may be reported in subframe 0 ofthe next frame, HARQ-ACK for PDSCH received in subframes 3 and/or 4 maybe reported in subframe 1 of the next frame, HARQ-ACK for PDSCH receivedin subframes 5 and/or 6 may be reported in subframe 2 of the next frame,HARQ-ACK for PDSCH received in subframes 7 and/or 8 may be reported insubframe 3 of the next frame, HARQ-ACK for PDSCH received in subframe 9and/or subframe 0 of the next frame may be reported in subframe 4 of thenext frame. In this example, the HARQ timing rules may be defined suchthat the time delay between PDSCH and the corresponding HARQ-ACK is atleast at least 4 subframes, but the value of the time delay may varyaccording to the subframe in which PDSCH is received. To ensure thatcontinuous transmission of PDSCH transmission without stalling thetransmissions due to lack of HARQ acknowledgements, the maximum numberof HARQ processes may be increased from 8 to a higher number, such as12. This may be enabled by increasing the size of the HARQ processfields, in the downlink control information from 3 bits to 4 bits.

The WTRU may thus be configured to use a different subframe offset forHARQ-ACK for different subframe subset configurations. For example, theWTRU may be preconfigured with multiple different value of k that may beused for determining the subframe(n+k) that is used for transmittingHARQ-ACK to a serving site that transmitted a DL transmission insubframe(n). Which value of k should be used for a given DL transmissionmay be dynamically indicated in the DCI that includes the downlinkassignment for subframe(n). In an example, the WTRU may be configured totransmit the HARQ-ACK in any valid UL subframe (e.g., the first valid ULsubframe) on or after subframe(n+k).

In an example, a WTRU may be preconfigured with a set of multiple valuesfor k, and each DL subframe may be associated with a corresponding(e.g., semi-statically configured) value for k. For example, subframe(0)of a frame may use a first value for k that results in a valid ULsubframe for transmitting HARQ-ACK, while subframe(1) of a frame may usea second value for k that results in a valid UL subframe fortransmitting HARQ-ACK, etc. In an example, for each DL subframe adifferent set of PUCCH resources may be used. For example, the WTRU maybe preconfigured with a set of PUCCH resources (e.g., N_(PUCCH) ⁽¹⁾)that are specific to a given DL subframe.

In an example, the value of N_(PUCCH) ⁽¹⁾ used for a given subframe maybe tied and/or otherwise mapped to the value of k used. For example, iffor a DL transmission in subframe(n) the WTRU is configured to sendHARQ-ACK in a valid UL subframe corresponding to subframe(n+k) or later,the actual offset between subframe(n) and the HARQ-ACK subframe may beused to determine the identity of the specific PUCCH resources utilizedin the subframe (e.g., mapped to the value of N_(PUCCH) ⁽¹⁾ that isused).

In an example, a WTRU may be configured with different and/orindependent values of k for each serving site. For example, the WTRU maytransmit HARQ-ACK for a DL transmission received in subframe(n) fromserving site i in subframe(n+k_(i)). The WTRU may transmit HARQ-ACK fora DL transmission received in subframe(m) from serving site j insubframe(m+k_(j)). Each serving site may configure the WTRU with one ormore values of k_(i) for example different values of k_(i) that may beused for different subframes.

In an example, the WTRU may report HARQ-ACK feedback in subframe(n+4).However, in determining which UL subframe corresponds to subframe(n+4),the WTRU may count valid UL subframes for the serving site to which theHARQ-ACK transmission is sent, not UL subframes that are not configuredin the subset for the serving site that transmitted the DL data.

Depending on the HARQ timing utilized at a given serving site and theconfiguration of the subframe subsets, situations may arise where theWTRU is configured to transmit multiple HARQ-ACKs in the same subframe.If the different HARQ feedback transmissions are being sent to differentserving sites, the WTRU may be configured to drop all but one HARQ-ACKtransmission (e.g., and transmit the undropped HARQ feedback in thedetermined subframe), while transmitting the dropped HARQ feedbackvalue(s) in the next allowed subframe(s). Which HARQ feedback should bedropped in a given subframe is to be dropped may be determined based ona priority ranking. The priority ranking may be preconfigured and/or maybe determined based on a characteristic of the DL data included in thetransmission for which the HARQ feedback is being sent. For example, thepriority ranking may be based on one or more of the identity of thebearer associated with the DL transmission, the message type of the DLtransmission, the amount/number of subframes since the data wasoriginally transmitted, and/or the like.

When transmitting the HARQ feedback, the WTRU may include a bit field toindicate whether or not HARQ-ACK was dropped in order to accommodate thecurrent HARQ feedback transmission. Further, a HARQ-ACK may beidentified with an index to indicate if it was to be delivered inanother subframe but was dropped (e.g., for example due to lowerpriority).

In an example, a WTRU may be configured to bundle HARQ-ACKs to betransmitted. For example, ACK-NACK bundling similar to those used forTDD HARQ operation may be used for a time segregation multi-serving siteFDD operation. In an example, multiplexing of HARQ-ACKs may be used inthe case of a collision between multiple HARQ-ACKs in the same subframe.

In an example, a first HARQ-ACK to be transmitted in a given subframemay be sent using a first set of PUCCH resources, while a secondHARQ-ACK to be transmitted in the given subframe may be sent using asecond set of PUCCH resources. The determination of which HARQ-ACKshould be assigned to a given PUCCH resource may be preconfigured and/ormay be determined based on a priority rule. For example, the prioritymay be based on which PDSCH transmission was received first in time bythe WTRU. In an example, if a single HARQ-ACK is to be transmitted in agiven subframe then the a single HARQ-ACK may be sent using a first setof PUCCH resources, and if two or more HARQ-ACKs are to be sent in thesubframe, the two or more HARQ-ACKs may be bundled or multiplexed thatare sent using another set of PUCCH resources. In an example, the numberof PUCCH resources included in a bundle may be used to determine whichPUCCH resource should be used. For example, one HARQ-ACK (e.g.,unbundled) may be sent using a first set of PUCCH resources, two bundledHARQ-ACKs may be sent using a second set of PUCCH resources, threebundled or multiplexed HARQ-ACKs may use a third set of PUCCH resources,and so on.

In an example where there may be overlap of UL subframes to multipledifferent serving sites, multiple HARQ-ACKs to different sites may beconfigured to be transmitted in the same subframe. If the WTRUdetermines that HARQ feedback is scheduled to be transmitted to multipleserving sites in the same UL subframe, the WTRU may use a priority ruleto determine a single HARQ-ACK to transmit while other HARQ feedback maybe dropped for that subframe. The priority rule may be preconfiguredand/or may depend on the identity of the serving site that transmittedthe DL data. In an example, the HARQ-ACKs for multiple serving sites maybe bundled or multiplexed and sent to a single serving site. Forexample, each HARQ-ACK may have an identifier to indicate for whichserving site the HARQ information is applicable to.

In an example, the WTRU may be configured to report Power Headroom (PH)and/or other power-related information such that the transmissions todifferent serving sites may be taken into consideration for powercontrol procedures implemented by the different serving sites. Forexample, the WTRU may be configured to send one or more power headroomreports (PHRs) to a serving cell of a given serving site/layer thatincludes PH information for that serving site layer as well as PHinformation related to transmission to a different serving site at adifferent serving site/layer.

For example, if the WTRU is transmitting a PHR that includes informationrelated to multi-layer operation, the PH and/or power-relatedinformation included in the PHR may be applicable to the subframe duringwhich a transport block that includes the report is transmitted. The PHRmay be generated taking into consideration any actual transmission thatis performed in the concerned subframe. The PHR may be generated takinginto consideration one or more hypothetical (and/or virtual)transmissions that could have been performed in the concerned subframe.For example, a PHR may be generated by the WTRU taking intoconsideration a UL transmission that may have been sent to an activatedserving cell for another serving site even if such a transmission wasnot actually sent in the subframe. If the transmission is not actuallysent, then the WTRU may use a predefined set of transmission parametersfor a hypothetical power usage determination and/or may use thetransmission parameters that correspond to the last transmissionperformed for the concerned PUSCH. If a previous transmission has notyet occurred since the other cell was activated, the WTRU may determineto not include a virtual transmission for such a PUSCH in the reportand/or use a predefined set of parameters for estimating powerinformation related to a hypothetical PUSCH transmission.

In an example, the PH and/or power-related information included in thereport may be applicable to WTRU operation in one or more subframe(s).For example, the PH and/or power-related information included in thereport may be applicable to the subframe in which the PH report istransmitted to the serving cell of a given serving site/layer. Forexample, sf0 may be used to represent the subframe during which thereport is transmitted. In an example, rather than or in addition to thePH and/or power-related information included in the report beingapplicable to subframe sf0, the PH and/or power-related informationincluded in the report may be applicable to last subframe before or atsubframe sf0 that satisfied one or more conditions. For example, the PHand/or power-related information included in the report may beapplicable to last subframe before or at subframe sf0 that was availablefor UL transmission to a second (e.g., different) serving site/layer. Inan example, the PH and/or power-related information included in thereport may be applicable to last subframe before or at subframe sf0 thatwas available for UL transmission to both the first serving site/layer(e.g., the serving site/layer to which the report is being sent) and asecond (e.g., different) serving site/layer. In an example, the PHand/or power-related information included in the report may beapplicable to a subframe in which a PUCCH transmission took place asecond (e.g., different) serving site/layer (e.g., possibly for PH type2, but not other PH types). In an example, the PH and/or power-relatedinformation included in the report may be applicable to a subframeduring which a PUSCH transmission was sent to a second (e.g., different)serving site/layer (e.g., possibly for PH type 1, but not other PHtypes). In an example, the PH and/or power-related information includedin the report may be applicable to a subframe during which ULtransmissions to both the first serving site/layer (e.g., the servingsite/layer to which the report is being sent) and a second (e.g.,different) serving site/layer actually took place. The PH and/orpower-related information included in the report may be applicable tothe last N subframe(s) before or at subframe sf0 that satisfied one ormore of conditions such as those described above, where the number ofsubframes N may be predefined and/or configured by higher layers. The PHand/or power-related information included in the report may beapplicable to the set of subframes within a period (e.g., schedulingperiod) ending before or at subframe sf0 that satisfy one or moreconditions such as those disclosed above.

If the number of subframes satisfying the criteria used for triggering aPHR is more than one, the value of the PH to be reported by may bedetermined as an average (e.g., linear or dB) of the PH values obtainedfrom the individual subframes. In an example, rather than or in additionto indicating the average value of the PH values for subframes thatsatisfied the reporting criteria, the WTRU may report a maximum PH valuefor the two or more subframes and/or a minimum value for the two or moresubframes. In an example, the WTRU may use one or more of an averagevalue, a maximum value, and/or minimum value of the PUSCH power and/orPUCCH power used in each subframe for which the reporting condition wassatisfied when determining the PH and/or power-related information toinclude in the report. By using one or more of an average value, amaximum value, and/or minimum value of the PUSCH power and/or PUCCHpower used in each subframe for which the reporting condition wassatisfied when determining the PH and/or power-related information toinclude in the report, the scheduling entity in a given serving site touse the information to make scheduling decisions taking into account thepossibility that the scheduling entity in the other serving sites mayschedule a transmission in the same subframe, even if the PHR wasscheduled in a subframe in which transmission from a single layer tookplace.

In an example, the PH and/or power-related information included in thereport sent to a serving cell of a given layer/serving site may includea type 1 PH and/or type 2 PH determined for the serving cell assumingtransmissions(s) to the serving cell to which the report is sent withoutaccounting for transmissions to serving cells located at other servingsites (e.g., using legacy PH determination methods). In an example, thePH and/or power-related information included in the report sent to aserving cell of a given layer/serving site may include the totaltransmission power on all serving cells of a given layer (e.g.,P_(ltot,l)). In an example, the PH and/or power-related informationincluded in the report sent to a serving cell of a given layer/servingsite may include a PH that is determined for a given layer taking intoaccount transmissions from all serving cells (and/or activated servingcells) of the layer. For example, the PH and/or power-relatedinformation included in the report may include a ratio and/or differencein dB between a total configured maximum output power for the WTRU (e.g.P_(cmax)) and the total transmission power on all serving cells of agiven layer (e.g., P_(ltot,l)). The PH and/or power-related informationincluded in the report may include a ratio and/or difference in dBbetween a total configured maximum output power for a given layer (e.g.,P_(lmax,l)) and the total transmission power on all serving cells of agiven layer (e.g., P_(ltot,l)).

In an example, the PH and/or power-related information included in thereport may include a new type of PH information determined for a servingcell of a first serving site/layer taking into account transmissionssent to a second serving site/layer. For example, a modified type 1(and/or type 2) PH may be determined based on an adjusted value of theconfigured WTRU transmit power in subframe i for serving cell c thattakes into account a possible reduction of available power in the firstlayer due to potential and/or actual transmissions in the second layer(P^(a) _(cmax,c(i))), for rather than the using the total configuredWTRU transmit power in subframe i for serving cell c (e.g.,P_(cmax,c(i))). For example, the adjusted value P^(a) _(cmax,c(i)) maybe a minimum between the total configured WTRU transmit power insubframe i for serving cell c (e.g., P_(cmax,c(i))) and the remainingavailable power for a layer in subframe I (e.g., P_(avail,l(i))). Theremaining available power for a given layer may be determined in linearunits as P{circumflex over ( )}_(cmax)−P{circumflex over ( )}_(ltot,m),where P{circumflex over ( )}_(cmax) may represent the total configuredmaximum output power for the WTRU (e.g., in linear units) andP{circumflex over ( )}_(ltot,m) may represent the total transmissionpower of each configured serving cells of a second layer m (and/or onall layers m other than first layer in case more than two layers areconfigured). The value of total transmission power of each configuredserving cells of a second layer m (e.g., P{circumflex over( )}_(ltot,m)) may be determined using one or more different methods.For example, the value of total transmission power of each configuredserving cells of a second layer m (e.g., P{circumflex over( )}_(ltot,m)) may be determined as the sum (e.g., in linear units) ofeach actual transmission on each of the configured serving cells oflayer m. In an example, the value of total transmission power of eachconfigured serving cells of a second layer m (e.g., P{circumflex over( )}_(ltot,m)) may be determined the sum of all actual and/or potentialtransmissions on each activated serving cell of layer m. In making thedetermination, a potential (and/or virtual) transmission of PUSCH and/orPUCCH (e.g., possibly according to predetermined parameters) may beassumed if an actual transmission was not performed in subframe i forone or more serving cells of layer m. In an example, the value of totaltransmission power of each configured serving cells of a second layer m(e.g., P{circumflex over ( )}_(ltot,m)) may be determined as the totalconfigured maximum output power for layer m (e.g., P{circumflex over( )}_(lmax,m) in linear units).

The WTRU may include PH information for each configured and/or activatedMAC instance in a PHR transmitted to a specific serving site. In anexample, the PH information may be reported for transmissions related toa PCell of each MAC instance, but not to SCells associated with the MACinstances.

In an example, the WTRU may be triggered to send PHRs to one or moreserving sites based on various criteria. For example, the WTRU may betriggered to send a PHR to one or more serving sites based on one ormore of MAC instance/layer activation, MAC instance/layer deactivation,applying power scaling to a transmission in a given layer, a QoSrequirement not being met in a given layer, and/or the like.

For example, the WTRU may be triggered to send a PHR to one or moreserving sites based on a MAC instance/layer being activated and/ordeactivated. For example, the WTRU may trigger a PHR to be sent based onWTRU receiving control signaling that configures a MAC instance of theWTRU configuration. In an example, the WTRU may be triggered to sendPHRs to one or more serving sites based on the WTRU removing a MACinstance that the WTRU was previously using and/or configured to use(e.g., following reception of control signaling deactivating the layer;the WTRU determining RLF for the concerned layer; other impairmentevents for the concerned layer; etc.). As an example, the WTRU may betriggered to send PHRs to one or more serving sites based on the WTRUreceiving control signaling that activates a MAC instance of the WTRUconfiguration. In an example, the WTRU may be triggered to send PHRs toone or more serving sites based on the WTRU deactivating a MAC instanceof the WTRU configuration. The deactivation may be based on reception ofcontrol signaling indicating the layer should be deactivate and/orfollowing the expiration of a timer indicting deactivation (e.g.,WTRU-autonomous deactivation). In an example, the WTRU may be triggeredto send PHRs to one or more serving sites based on the WTRU receivingcontrol signaling that schedules the first transmission for a concernedMAC instance after the concerned MAC instance was last configured and/oractivated (e.g., the first PUSCH transmission). In an example, the WTRUmay be triggered to send PHRs to one or more serving sites based on theWTRU receiving control signaling that schedules the first transmissionfor a MAC instance/layer since the WTRU last deactivated, removed,and/or otherwise invalidated one or more other MAC instances (e.g., thefirst scheduled PUSCH transmission).

In an example, the WTRU may be triggered to send PHRs to one or moreserving sites based on applying power scaling to one or moretransmissions to a given serving site/in a given layer. In an example,rather than or in addition to being triggered to send the PHR based on asingle occurrence of power scaling, the determination of whether or notto trigger a PHR may be determined based on transmissions occurring overa given period (e.g., for a scheduling period and/or for a configuredamount of time) during which power scaling has applied. For example, ifthe WTRU scales a certain number of consecutive transmissions and/orscales each transmission to a given serving site that occurs within apredetermined time period, the WTRU may determine to send one or morePHRs. In an example, the PHR may be triggered due power scaling oncondition that the power scaling is applied to transmissions for a LCHand/or for a MAC instance of a priority higher than a given orconfigured threshold.

In an example, the WTRU may be triggered to send PHRs to one or moreserving sites based on a QoS requirement (e.g., PBR, latency, etc.) notbeing met in a given layer. For example, the WTRU may be triggered tosend PHRs to one or more serving sites based on the WTRU determiningthat a power limitation being applied in a given layer and/or theapplication of a power scaling function in a given layer precludesand/or otherwise restricts a WTRU from satisfying one or more QoSrequirements of LCH and/or MAC instance. For example, the WTRU maydetermine that the application of the power scaling may prevent a QoSrequirement such as a latency requirement and/or a PBR requirement frombeing met. In an example, rather than or in addition to being triggeredto send the PHR based on a single occurrence of a QoS requirement notbeing met, the determination of whether or not to trigger a PHR may bedetermined based on transmissions occurring over a given period (e.g.,for a scheduling period and/or for a configured amount of time) duringwhich the QoS requirement was not met. Whether or not a QoS requirementis met may be determined for a given period, e.g., for a schedulingperiod and/or for a specific (possibly configured) amount of time. Forexample, if the WTRU determines that a QoS requirement was not met for anumber of consecutive transmissions and/or for transmissions occurringwithin a predetermined time period, the WTRU may determine to send oneor more PHRs. In an example, the PHR may be triggered due a QoSrequirement not being met on condition that the QoS requirement isapplicable to transmissions for a LCH and/or for a MAC instance of apriority higher than a given or configured threshold.

Irrespective of the criteria that triggered PHR transmission, the PHRmay be sent to the concerned serving site and/or one or more otheractive serving sites (e.g., on the resources of another MAC instance).The PHR may be provided to other serving sites such that schedulers atthe different serving sites may determine from the received PHR(s) thatthe power conditions may have changed for the WTRU due to an event thatoccurred in another layer (e.g., controlled by a second scheduler). ThePHR sent to the different serving sites may include common PHRinformation (e.g., information applicable to each of the serving sites),serving site specific PH information, and/or PH information applicableto other serving sites.

In an example, the WTRU may be configured to report a number ofparameters related to Quality of Service (QoS) to one or more servingsites. Reports relating to QoS parameters for one or more serving sitesmay be referred to as QoS-related status reports (QSRs). From thenetwork perspective, QSR reporting may be useful for a schedulerassociated with a first layer in that the scheduler for the first layermay determine the impact (e.g., how well QoS is served) of thescheduling and/or radio quality experienced by the WTRU from anotherlayer and/or from the combined transmission efforts of each of thelayers utilized by the WTRU (e.g., including the first layer).

For example, a scheduler located at a first serving site correspondingto a primary layer may receive a QSR from a WTRU. The QSR may includeinformation related to transmissions in the primary layer and/ortransmission in other layers. The QSR may indicate that one or more QoSrequirements are not being met for one or more DRBs configured for theWTRU. The scheduler in the primary layer (e.g., the scheduler for thefirst serving site) may determine that one or more action should beperformed in order to ensure QoS requirements for the WTRU are beingmet. For example, if the DRB for which a given QoS requirement is notbeing met is associated with a secondary layer transmission (e.g., notwith primary layer transmission), the scheduler located at a firstserving site corresponding to a primary layer may implement one or moreactive queue management procedures such that the data rate of theapplication generating that data may be reduced in the WTRU (e.g., usingexplicit congestion notification (ECN) marking, by selectively droppingpackets, etc.). In an example, if the DRB for which a given QoSrequirement is not being met is associated with a secondary layertransmission (e.g., not with primary layer transmission), the schedulerlocated at a first serving site corresponding to a primary layer maytrigger mobility-related measurements to be performed by the WTRU in thesecondary layer. In an example, if the DRB for which a given QoSrequirement is not being met is associated with a secondary layertransmission (e.g., not with primary layer transmission), the schedulerlocated at a first serving site corresponding to a primary layer mayinitiate mobility for the concerned DRB such that the DRB is moved toanother layer (e.g., the primary layer). In an example, if the DRB forwhich a given QoS requirement is not being met is associated with asecondary layer transmission (e.g., not with primary layertransmission), the scheduler located at a first serving sitecorresponding to a primary layer may reconfigure the DRB such thatmulti-layer flow is supported for the logical channel served by the DRBsuch that the data for which the QoS requirement is not being meth maybe sent using a one or more of plurality of layers. In an example, ifthe DRB for which a given QoS requirement is not being met is associatedwith a secondary layer transmission (e.g., not with primary layertransmission), the scheduler located at a first serving sitecorresponding to a primary layer may notify the MME/NAS such that theservice may be reconfigured. As an example, if the DRB for which a givenQoS requirement is not being met is associated is configured such thatmulti-flow is supported, rather than or in addition to performing one ormore of the actions described with respect to a DRB mapped to asecondary layer, the scheduler located at a first serving sitecorresponding to a primary layer may allocate additional resources forthe concerned DRB in the primary layer.

A QSR may contain a variety of QoS-related information. For example, aQSR may include a timing-related value such as a head of queue delay(e.g., QSR/Delay). For example, the QSR may include a value related tothe time that data has spent in a WTRU buffer measured from an arrivaltime until a current time. For example, the arrival time may correspondto the time the data was first made available for transmission. Thecurrent time may correspond to the time when the report was triggered,the time when the corresponding MAC PDU was assembled, and/or the timewhen the corresponding MAC PDU was first transmitted. The timing relatedvalue included in the QSR may correspond to the maximum delay that mayelapse before data in a WTRU buffer (e.g., a SDU or a PDU) should betransmitted. For example, the QSR may indicate the shortest value forthe maximum delay that may elapse before data in a WTRU buffer (e.g., aSDU or a PDU) should be transmitted. For example, the time related valuemay correspond to a value associated with a PDCP DiscardTimer (e.g., fora given radio bearer). The WTRU may determine and report a valuecorresponding to the difference between DiscardTimer and the differenceof the arrival time and the current time (e.g., reportvalue=DiscardTimer−(Arrival Time−Current Time)). In an example, the QSRmay include the time of stay in the WTRU buffer for the oldest data thatis buffered for transmission.

The QSR may include one or more a transfer rate related values such asindications of PBR satisfaction (e.g., QSR/PBR). For example, the QSRmay include an indication of whether or not the PBR is being met for oneor more DRBs/logical channels for which the QSR is applicable. Forexample, the QSR may include an indication of failure to satisfy a PBRfor one or more logical channels/DRBs and/or an indication of how muchadditional data would have to be transmitted (e.g., within a specifiedtime period) in order to satisfy a given PBR. For example, the reportmay include an indication that the PBR one or more LCHs and/or anaggregated PBR for one or more LCGs has not been met. The WTRU maydetermine whether or not PBR dissatisfaction should be reported when thePBR has not been met for a specific (e.g., configurable) period of time.As an example, the QSR may include a value that corresponds to theminimum amount of data that would have to be transmitted for a givenLCH/LCG in order for the WTRU to meet the corresponding PBR. The WTRUmay include an indication of the identity of the LCH and/or the LCG forwhich a PBR is not being met in the QSR. In an example, the QSR mayidentify the LCH and/or LCG which includes the largest amount of datafor which a PBR is not being met. When information for multiple LCHsand/or LCGs may be included in the same report, each reported item maybe indicated in decreasing order of the size of the data for which thePBR is not being met and/or as an ordered list of the affected entities.The WTRU may determine whether or not a value should be reportedindicating the amount by which the PBR requirement is not being met, forexample based on the PBR not having been met for a specific (e.g.,configurable) period of time.

The period of time over which the WTRU may perform the evaluation ofwhether QoS requirements are met for formulating QSRs may be a functionof the length of a scheduling period, for example if the WTRU isconfigured such that multiple layers operate using different schedulingperiods.

The contents of a QSR may be associated with and/or applicable to one ormore radio bearers configured for the WTRU. For example, the QSR may beWTRU-specific and may include information that is applicable to aplurality (e.g., all) of the bearers configured for use by the WTRU. TheQSR may be layer-specific and may include information that is applicableto a plurality (e.g., all) of the bearers associated with a specific MACinstance (e.g., with a secondary MAC instance). The QSR may begroup-specific, for example reporting information for radio bearers thatare configured as part of a LCG. For example, the QSR may include onevalue for each LCG included in the QSR. In an example, rather than or inaddition to using logical channel groups, the QSR may group one or morelogical channels or radio bearers in a different manner. A QSR may bepriority-specific. For example, a given QSR may be associated with radiobearers corresponding to a specific priority level and/or radio bearerscorresponding to a priority level equal to or above a configuredthreshold. A QSR may include a report for radio bearers (RBs) associatedwith and/or configured for multi-flow operation. For example, data fromradio bearers associated with and/or configured for multi-flow operationmay be transmitted on the radio resources of a plurality of MACinstances. A QSR may include a report for a specific type of RB, forexample DRBs, SRBs, DRBs and SRBs, etc. In an example, the QSR sent bythe WTRU may include one value for each instance of a specific reportingtype (e.g., WTRU-specific, layer-specific, group-specific,priority-specific, multi-flow specific, type of RB-specific, etc.). Forexample, if the report is layer specific, a single QSR value may bereported for each layer. If the report is priority specific, a singleQSR value may be reported for each priority.

The WTRU may be triggered to transmit a QSR based on detecting variouscriteria or conditions. For example, the WTRU may be configured toperiodically generate and/or transmit a QSR. For example, the WTRU maybe configured with a value for a QSR timer and may be triggered totransmit a QSR upon expiration of the timer. The timer may be startedand/or restarted each time the QSR is triggered and/or transmitted. Inan example, the WTRU may be configured to trigger a QSR based on one ormore thresholds being exceeded. For example, a WTRU may be configured togenerate and/or transmit a QSR based on one or more QoS parameters beingbelow a certain threshold (e.g., the threshold may be a part of the WTRUconfiguration set by the network). For example, the WTRU may trigger aQSR that includes PBR information based on the PBR for one or morelogical channels/logical channel groups falling below a threshold, whichmay be configured threshold. A QSR including PBR related information(e.g., QSR/PBR) may be triggered when PBR is not met and/or is below athreshold for a specified/configurable amount of time. In an example,the WTRU may be triggered to send a QSR that includes delay relatedinformation (e.g., QSR/Delay) when an acceptable delay for one or moreitems (e.g., LCH, LCG, etc.) falls below a specified/configuredthreshold. For example, a QSR may be transmitted for a given radiobearer based on the WTRU determining that the difference between a valueof the DiscardTimer and (Arrival Time−Current Time) (e.g., as describedabove) becomes less than a threshold.

In an example, the WTRU may be triggered to generate and/or send a QSRbased on determining that the radio link conditions have or aredeteriorating below a specified/configured threshold. In an example, theWTRU may be triggered to generate and/or send a QSR based on determiningthat one or more RRC timers are running for a given MAC instance. Forexample, a QSR may be sent to a serving site for a MAC instance forwhich T301, T302, T304 and/or T311 is running. The QSR may be sent tothe MAC instance for which the RRC timer(s) is running and/or to adifferent MAC instance. In an example, the QSR may be triggered based onthe RRC timer(s) running in a secondary MAC instance (e.g., if the WTRUhas an ongoing procedure related to connectivity, mobility and/orre-establishment in a secondary layer), but not for RRC timer(s) runningin a primary MAC instance.

In an example, the WTRU may be triggered to generate and/or send a QSRbased on receiving an aperiodic QSR request from one or more of theserving sites. The WTRU may be triggered to send a QSR upon request fromthe network, and the request may be included control signaling (e.g., aMAC CE) that requests such a report. The control signaling may beinclude in L1 signaling (e.g., as a flag in a DCI format) and/or in aMAC CE (e.g., as a flag in a MAC CE, possibly including an explicitindication of the radio bearers for which the QSR should be sent).

In an example, the WTRU may be triggered to generate and/or send a QSRbased on reception of control signaling that deactivates a MAC instance(e.g., upon deactivation of a secondary MAC instance). For example, theQSR may be generated based on a MAC instance being deactivated whilethere is still some data in the WTRU buffer(s) for the deactivated MACinstance. In an example, the QSR may be triggered if the WTRU has databuffered for a LCH/LCG associated with the deactivated MAC instance thatis not mapped to any other layers. Such a QSR may be a trigger for radiobearer mobility for radio bearers of the deactivated MAC instance. In anexample, the WTRU may be triggered to generate and/or send a QSR formulti-flow bearers (e.g., bearers mapped to multiple MACinstances/layers) that were utilized by a deactivate MAC instance. Sucha QSR may be used to make scheduling adjustments due to the change ofavailable resources for a given WTRU.

In an example, the WTRU may be triggered to generate and/or send a QSRbased on reception of control signaling that activates a MAC instance(e.g., upon activation of a secondary MAC instance). For example, uponactivation of a MAC instance, the WTRU may determine that it has databuffered for transmission and may send the QSR in order to triggerbearer mobility to the newly activated MAC instance. In an example, theWTRU may be triggered to generate and/or send a QSR based on a BSR beingtriggered.

In an example, if the WTRU determines that a given MAC instance is nolonger suitable for meeting one or more QoS requirements of a multi-flowbearer (e.g., due to deactivation, deteriorating radio link quality,RLF, RLM, reset and/or removal of the MAC instance, etc.), the WTRU maytrigger a QSR in one or more other layers mapped to the multi-flowbearer in order to be scheduled such that the QoS requirements may besatisfied using the resources of other layer(s).

For example, if the WTRU determines that a MAC instance has become apotential candidate for improving the QoS of a multi-flow bearer (e.g.,due to activation, improving radio link quality, configuration of theMAC instance, etc.), the WTRU may trigger a QSR to that MAC instancesuch that the MAC instance may be scheduled for that bearer. The WTRUmay include a QSR report (e.g., a short version of a QSR report) insteadof padding (e.g., which may have a lower priority than a padding BSR),if a QSR report may fit in a given transport block.

One or more triggers for sending QSRs may be subject to a backoff and/orprohibit mechanism (e.g., that prevents the QSR from being sent unlessvarious other criteria are met), such as a timer. For example, if abackoff timer is running when the QSR is generated, the QSR may not besent until the timer has expired. The value used and/or the identity ofthe backoff and/or prohibit mechanism may be configured on WTRU-specificbasis, a layer-specific basis, a group-specific basis, apriority-specific basis, a multi-flow specific basis, a type ofRB-specific basis, and/or the like. When a QSR is triggered, the WTRUmay start a timer and may be prohibited from triggering additional QSRuntil the timer has expired.

The WTRU may trigger a Scheduling Request (SR) when it triggers a QSR.For example, the SR may be triggered for the MAC instance and/orinstances for which the QSR is applicable. As an example, the WTRU maytrigger a SR according to which MAC instance may be used to transmit thedata that triggered the QSR. For example, the resource (e.g., PUCCH,PRACH, etc.) and/or method (e.g., D-SR, RA-SR, etc.) used for the SR maybe selected as a function of the MAC instance associated with the SRtransmission and/or QSR transmission (e.g., the MAC for a specific layerif multi-flow is not supported for the concerned RB, otherwise eitherMAC instance).

In an example, when a QSR report is triggered, it may be pending untilit is cancelled. The QSR report may be pending for a specific layerand/or for multiple layers. A QSR report may be cancelled based on theoccurrence of one or more events. For example, the WTRU may cancel apending and/or triggered QSR based on the QSR being included in a MACPDU for transmission on a transport block. In an example, the WTRU maycancel a pending and/or triggered QSR based on the criteria thattriggered QSR to be sent no longer being met. For example, the WTRU maycancel a pending QSR/Delay report if the corresponding data is no longerin the WTRU buffer (e.g., the data was included in a transport block fortransmission; the data has been discarded, etc.). F In an example, theWTRU may cancel a pending and/or triggered QSR based on a sufficientamount of data from buffer associated with the QSR (e.g., LCH and/orLCG) being include in transport block for transmission. In anotherexample, the WTRU may cancel all pending and/or triggered QSRs for a MACinstance based on the concerned MAC instance being reset, deactivated,and/or removed from the WTRU configuration. For example, the WTRU maycancel a QSR to be transmitted to a given serving site for a given DRBbased on the upon radio bearer mobility that moves the DRB to anotherlayer. In an example, the WTRU may cancel a pending and/or triggered QSRbased on a MAC instance associated with the corresponding reporting itembeing activated (e.g., in case activation may be in response toimprovement of the QoS of the WTRU). In an example, the WTRU may cancelall pending (and/or triggered) QSR to be transmitted for a given MACinstance based on the WTRU receiving a reconfiguration of the concernedMAC instance that modifies and/or removes the radio bearer or bearersthat triggered the QSR (e.g., upon radio bearer mobility that moves thebearers to another layer or that reconfigures the corresponding QoSparameters).

When a QSR is pending, the QSR may be transmitted when a transport blocksatisfies the requirement for the QSR transmission. The WTRU mayevaluate the above canceling criteria by including the impact of atransport block to be transmitted up to and including those of thesubframe in which the concerned QSR would have been transmitted. In anexample, the WTRU may cancel a pending SR that was triggered by a QSR,if the QSR for the concerned SR is cancelled.

In an example, a QSR may be reported using specific resources from oneor more layers of the WTRU configuration. The selection of which MACinstance may transfer QSR may be indicated in a received configurationfor a given bearer and or a received configuration for a given MACinstance. In an example, the selection of which MAC instance is to beused for transmitting a QSR may be based on one or more of whether theQSR is layer specific, whether a transport block is being delivered to aprimary layer, and/or whether the QSR is to be duplicated acrossmultiple layers. For example, a QSR may be reported in a transport blockassociated with a layer for which the information included in the QSR isapplicable. As in example, the QSR may include information associatedwith a specific DRB, and the QSR may be transmitted to the layer mappedto the concerned DRB. In an example, QSRs may be reported in a transportblock associated with a primary layer (e.g., with a layer used forconnectivity that may be associated with a MeNB), but not in a secondarylayer. As another example, when triggered, a QSR may be duplicated suchthat it may be included in at least one transport block associated witheach layer to which the QSR is applicable.

In an example, Buffer Status Reporting (BSR) may include the triggeringof a BSR and/or determination of the contents of the concerned BSR. TheWTRU may determine whether or not a BSR should be triggered based on oneor more criteria. For example, the WTRU may evaluate the criteria fortriggering a BSR by applying the criteria to a subset of logicalchannels (LCHs) and/or LCH groups (LCGs). For example, the WTRU mayreceive a configuration for a LCH and/or a LCG that includes anassociation with the subset of LCHs and/or LCGs. A LCH may be associatedwith a plurality of subsets (e.g., by being configured such that it maybe associated with more than one LCG). In an example, the WTRU mayevaluate the criteria for triggering a BSR on a per MAC instance and/orlayer-specific basis (e.g., by applying the criteria to the set ofLCH(s) and/or LCGs of a given MAC instance).

The WTRU may be configured with a DRB such that multi-flow operation issupported for the corresponding DRB. For example, multi-flow may beachieved by configuring a DRB with a LCH that is mapped to a pluralityof MAC instances. In an example, multi-flow may be achieved byconfiguring one DRB for a given EPS bearer, and one DRB for eachconcerned MAC instance. The DRB may then be grouped with one or moreother DRB such that a plurality of DRB configurations are associatedwith a LCG, where the LCG may in turn be associated with thecorresponding plurality of MAC instances.

A BSR may be triggered if a QoS requirement of a LCH and/or a LCG is notmet (e.g., PBR, or latency/delay etc.). In an example, a BSR may betriggered for a LCH/LCG configured for multi-flow operation, but not forsingle flow LCH/LCG.

When a BSR is triggered, the WTRU may trigger a SR on the MAC instanceto be used to transmit the data that triggered the BSR. For example, theresource (e.g., PUCCH, PRACH, etc.) and/or method (e.g., D-SR, RA-SR,etc.) used to send the SR may be selected as a function of the MACapplicable for such transmission. A BSR may be extended to include oneor more QSR values. For example, for each LCH/LCG reported in a BSR, theWTRU may include a value for a QSR applicable to the reported LCH/LCG.

The WTRU may duplicate a BSR if the BSR includes a report for at leastone radio bearer for which multi-flow is configured. For example, if aradio bearer is a multi-flow bearer, a BSR is transmitted on each layerthat is applicable to the concerned multi-flow bearer.

In an example, the WTRU may perform logical channel prioritization (LCP)as a function of a priority association between different layers (e.g.,different serving sites, different schedulers, different MAC instance,etc.). When a LCH is configured for multi-flow operation, the LCH may beassociated with and/or may be allocated resources of a plurality of MACinstances (e.g., may be scheduled resources on different layers). Inorder to account for multi-layer transmission, a logical channelprioritization procedure may involve applying prioritization rulesacross a plurality of MAC instances. For example, a PBR and/or a logicalchannel priority for a given LCH may be assigned on a per layer basis(e.g., the PBR and/or logical channel priority for a multi-flow bearermay be different for different MAC instances). The PBR and/or logicalchannel priority of a given logical channel may be associated withWTRU-specific maximum values (e.g., although PBR/logical channelpriority may be layer specific, the values for the PBR/logical channelpriority may not exceed the corresponding WTRU-specific maximum in anyof the layers). Data from a multi-flow LCH may contend for resources inany layer for which the multi-flow LCH is configured. When allocatingresources of a transport block for transmissions, the WTRU may allocateresources to one or more logical channels in priority order up to theconfigured PBR(s) for the logical channels. If the PBR for each of thelogical channels is satisfied and there are remaining resources in thetransport block for a MAC instance, the LCHs with remaining databuffered for transmission may be served in strict priority order untilthe transport block is full or there is no remaining data for any of thelogical channels. Such PBR and/or priority rules may be layer-specific,and a given multi-flow LCH may have the same or a differentconfiguration (e.g., PBR, priority, etc.) for each layer. As an example,the PBR for a given LCH (e.g., a multi-flow logical channel mapped to aplurality of MAC instances) may be capped across the plurality of layersassociated with the logical channel. Rather than or in addition to aWTRU-wide PBR cap for a multi-flow logical channel, the logical channelmay also be configured with layer-specific PBR(s) that may cap theprioritized transmissions for the logical channel on a specific MACinstance.

Data from a multi-flow LCH may contend for resources in one or moreapplicable layers. The WTRU may allocate resources of a transport blockto the LCH up to the configured PBR (e.g., a layer specific PBR and/or aWTRU-wide PBR). If a given PBR is WTRU-specific or WTRU-wide (e.g., thePBR may be applicable to any MAC instance and/or may be decremented whenthe logical channel is served resources by any of the MAC instances), ifthe WTRU-specific PBR is satisfied in using a subset of the layers towhich the LCH is mapped, the LCH may not be allowed to contend forresources in the remaining layers (e.g., even if a layer-specific PBRhas not been met) until the PBRs for other logical channels have alsobeen satisfied. However, even if the WTRU-specific PBR has been reached,if for a certain MAC instance the PBR of each of the logical channelsserved by the MAC instance has been satisfied (e.g., no other LCH forthe concerned layer has bj>0), if resources remain in the transportblock for the layer, the logical channel may be served additionalresources in excess of its WTRU-specific PBR even though theWTRU-specific PBR of other logical channels has not yet been reached(e.g., the logical channels whose WTRU-specific PBR has not yet beensatisfied may not be mapped to the MAC instance with remaining resourcesin the transport block).

As an example, a change in the state of a MAC instance may trigger oneor more changes to the logical channel prioritization configuration fora multi-flow LCH served by that MAC instance. For example, data from amulti-flow LCH may contend for resources in one or more layers. Whenfirst serving the plurality of logical channels for a newly formedtransport block, the WTRU may allocate resources to the multi-flow LCHup to its configured PBR, which may include a WTRU-specific PBR for theLCH and/or a plurality of layer-specific PBRs (e.g., the WTRU may servethe logical channel based on a sum of a number of aggregated PBRconfigurations). However, during certain periods one or more of thelayers that may be unavailable, for example due to the state of theassociated MAC instance (e.g., the MAC instance may be in a deactivatedstate, the MAC instance may be in an impaired state due to poor radioconditions, etc.). In such a scenario, the WTRU may be configured totrigger a QSR/PBR for one or more logical channels mapped to a layer forwhich the state change has occurred. The logical channel may bereconfigured in order to provide additional resources on other layerssince the logical channel may be inadequately served on the layer onwhich the MAC instance state change occurred. While this may starveother LCHs of lesser priority for the layers over which the logicalchannel was reconfigured (e.g., priority and/or PBR was increased), thescheduler for the concerned MAC instance may also reconfigure one ormore other logical channels to taken into account changes to the logicalchannel configuration of the multi-flow bearer/LCH.

As an example, the state of a MAC instance for the purposes of logicalchannel configuration may be determined based on the activation state ofthe MAC instance and/or based on the radio link conditions beingexperienced by the MAC instance. For example, a MAC instance may beunavailable when either the MAC instance is deactivated and/or all ofthe serving cells of the MAC instance are deactivated. A MAC instancemay be considered deactivated based on one or more of the radio linkconditions being below a given threshold, detecting radio link problemsduring a radio link monitoring procedure, determining that the estimatedpathloss exceeds a given threshold, determining that one or more cellsassociated with the concerned MAC instance is experiencing RLF (e.g.,one of or more of UL RLF and/or DL RLF), determining that RRC timer T310is running, determining that one or more of RRC timer T301, T302, T304,and/or T311 is running, and/or the like. In an example, rather thanconsideration each of the cells of the MAC instance to determine if theMAC instance is deactivated, the WTRU may consider the primary MACinstance.

From the network perspective, layer-specific priority allocation for amulti-flow LCHs enable the network to have some form of control overwhich layer is used first for transmitting data for a corresponding LCH.For example, a layer-specific PBR may enable the network to split theburden of meeting the QoS requirements between a plurality of layers,which may assist the network in allocating sufficient resources for themulti-flow bearer without having to starve one or more otherbearers/LCHs that are also served by the layers associated with themulti-flow logical channel.

In an example, when a new transmission is performed, the WTRU maydetermine an order of use for resources available on multiple layers.For example, the WTRU may assign an order for assigning data of alogical channel to transport blocks for transmission to over a givenlayer in a given time interval. For example, the time interval may beone of a TTI/subframe, a scheduling period (e.g., multiple subframes),and/or some other predefined period of time. In this manner, a prioritymay be applied to the different transport blocks of different layerssuch that a higher priority transport block/layer may be served withdata of a given multi-flow logical channel before data of the multi-flowlogical channel is served to a transport block of another, lowerpriority layer.

When there are transport block resources available to the WTRU in amultiple of layers, the WTRU may first allocate resources of a layerwith higher priority (e.g., a primary layer) during the logical channelprioritization process. When all resources of the layer with highestpriority have been allocated, the WTRU may allocate resources of otherlayers (e.g., a secondary layer) in decreasing priority (e.g., withequal priority layers being served concurrently). When the WTRU isallocates resources of a given layer of higher priority, the logicalchannel prioritization procedure may be performed first for thetransport block of the layer, and when the logical channelprioritization procedure for that logical channel is complete, the WTRUmay perform the logical channel prioritization for a lower prioritylayer with a transport block available for transmission. For example,consider the scenario where a WTRU is configured for use in a primarylayer (e.g., a serving site associated with a MeNB) and a secondarylayer (e.g., a serving site associated with a SCeNB). The primary layermay have a higher priority for purposes of logical channelprioritization than the secondary layer (or vice versa). In a schedulingperiod (e.g., subframe) during which both the primary layer andsecondary layer have a transport block scheduled for transmission, theWTRU may determine to first fill the transport block of the primarylayer, followed by the transport block of the secondary layer.

For example, the WTRU may first serve each of the logical channels thatare mapped to the primary layer up to their configured PBR (e.g., aWTRU-specific PBR and/or a layer-specific PBR) in order of logicalchannel priority. If there is remaining space in the transport blockafter each of the logical channels mapped to the primary layer have beenserved up to their configured PBR (e.g., a WTRU-specific PBR and/or alayer-specific PBR), the logical channels mapped to the primary layermay be served in strict priority order until all their data has beenserved. Once the transport block for the primary layer is filled, theWTRU may begin serving data to the transport block of the secondarylayer. For example, the WTRU may first serve each of the logicalchannels that are mapped to the secondary layer up to their configuredPBR (e.g., a WTRU-specific PBR and/or a layer-specific PBR) in order oflogical channel priority. One or more of these logical channels may bemulti-flow logical channels that were also served transmission resourcesin the transport block of the primary layer. If there is remaining spacein the transport block after each of the logical channels mapped to thesecondary layer have been served up to their configured PBR (e.g., aWTRU-specific PBR and/or a layer-specific PBR), the logical channelsmapped to the secondary layer may be served in strict priority orderuntil all their data has been served to the transport block of thesecondary layer.

In an example, the WTRU may be configured to first allocate resources tothe LCHs that are associated solely to a single MAC instance prior toserving a multi-flow logic channel when filling a transport block of thesingle MAC instance.

In an example, the WTRU may be configured with a first configuration(e.g., a layer-specific configuration) for performing logical channelprioritization. The first configuration (e.g., a layer-specificconfiguration) may include one or more of a PBR configuration (e.g.,prioritizedBitRate, bucketSizeDuration, etc.), a priority for a one ormore radio bearer and/or logical channel (LCH), and/or the like. Forexample, the first configuration may be received for a LCH that isconfigured for multi-flow operation.

When the WTRU is configured with such first configuration, the WTRU mayallocate resources to the logical channel by performing logical channelprioritization for resources of each layer according to a specificorder, (e.g., a priority order). In an example, the WTRU may performlogical channel prioritization independently for each layer, such thatLCHs configured for operation using a single layer may be servedaccording to legacy LCP procedures. Multi-flow LCHs may be configuredwith a layer specific PBR configuration such that the multi-flow channelis considered a single flow logical channel in a given layer whenapplying the layer-specific PRB configuration for that layer to thelogical channel for purposes of logical channel prioritization.

Rather than or in addition to the first configuration, the WTRU may beconfigured with a second configuration (e.g., a WTRU-specificconfiguration) that may include a PBR configuration and/or a priorityfor one or more radio bearers and/or logical channels. The secondconfiguration may be applicable to multi-flow logical channels and maybe used to define PBR rules for logical channels that may be served bymultiple layers. The second configuration may be in addition to a firstconfiguration or by itself as the entire configuration for the LCH.

When the WTRU is configured with a second, WTRU-specific logical channelconfiguration, the WTRU may allocate resources to the logical channel byperforming logical channel prioritization for resources of each layeraccording to a specific order (e.g., serve highest priority layer first,next highest second, etc.). The WTRU may perform logical channelprioritization for each layer such that LCHs configured for operationusing a single layer may be treated according to the legacy LCPprocedure. In an example, a LCH configured for multi-flow operation maybe considered for once per scheduling instance, and once the WTRU hasbeen allocated resources in a single (e.g., highest priority) layeraccording to its second configuration, the multi-flow logical channelmay not be considered for transmission in the secondary layer. In anexample, a LCH configured for multi-flow operation may be allowed toutilize the resources of multiple layers in a given scheduling period,provided the second configuration is applied across the plurality oflayers.

In an example, the WTRU may receive downlink control signaling (e.g.,such as DCI on the E-PDCCH and/or the PDCCH) that instructs the WTRU toassign the corresponding grant to a specific subset of LCHs. Forexample, the received DCI may include an indication such that thereceived grant may be used for transmission of data from one or more ofa specific LCH(s) (e.g., based on bearer identity), a specific bearertype (e.g., SRB), a specific priority (e.g., such as a WTRU-specific LCHpriority), and/or the like.

In an example, the WTRU may determine that it has not received (e.g.,successfully decoded) downlink control signaling for a control channel(e.g., PDCCH, ePDCCH, etc.) applicable to a certain MAC instance for acertain period of time. In an example, the WTRU may override one or morelogical channel prioritization rules based on determining that one orlayers have not been scheduled and/or one or more logical channels havenot been allocated resources for a predetermined period of time. Forexample, when the WTRU determines that it has not received a DCI of aspecific type such as a grant (e.g., a DCI for an allocation of uplinkresources for transmission in the concerned MAC) during the said periodof time, the WTRU may determine to override one or more logical channelperiodization rules. The LCH prioritization may be overridden based onthe WTRU failing to receive any DCI on a concerned MAC instance for aspecified period of time. In such a case, the WTRU may determine thatthe concerned MAC instance is no longer applicable for the LCP process.For example, the WTRU may perform LCP assuming the concerned MACinstance is in a deactivated state.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

What is claimed:
 1. A method implemented by a wireless transmit/receiveunit (WTRU), the method comprising: the WTRU utilizing a first physicallayer configuration for transmissions associated with a first data pathassociated with a first group of cells, wherein the first group of cellscomprises a primary cell and zero or more secondary cells and utilizes afirst radio access technology, and wherein the first physical layerconfiguration is configured for frequency division duplexing (FDD) ofthe transmissions exchanged with at least the primary cell of the firstgroup of cells; the WTRU utilizing a second physical layer configurationfor transmissions associated with a second data path associated with asecond group of cells, wherein the second group of cells comprises aprimary cell and zero or more secondary cells and utilizes a secondradio access technology, and wherein the second physical layerconfiguration is configured for time division duplexing (TDD) of thetransmissions exchanged with at least one of the primary cell and thezero or more secondary cells; the WTRU allocating a first transmissionpower for a first transmission to be sent to the primary cell of thefirst group of cells via the first data path and a second transmissionpower for a second transmission to be sent to the at least one of theprimary cell and the zero or more secondary cells via the second datapath, wherein: the first and second transmissions at least partiallyoverlap in time; and at least a portion of one or more of the firsttransmission power and the second transmission power is allocated basedon (i) whether the first and second transmissions are to be sent oncarriers within the same frequency range or on carriers within differentfrequency ranges, (ii) first and second independent maximum transmitpowers for constraining the first and second transmission powers,respectively, and (iii) one or more priority rules related to the firsttransmission being sent via the first data path and the secondtransmission being sent via the second data path; and the WTRUtransmitting the first and second transmissions using respective Uuinterfaces.
 2. The method as in claim 1, wherein a first of the one ormore priority rules comprises prioritizing a transmission that includesuplink control information (UCI) over a transmission that does notinclude UCI.
 3. The method as in claim 2, wherein a second of the one ormore priority rules comprises prioritizing a transmission that includesa first type of UCI over a transmission that includes a second type ofUCI.
 4. The method as in claim 3, wherein the first type of UCIcomprises hybrid automatic repeat request (HARQ) feedback and the secondtype of UCI comprises channel quality information (CQI).
 5. The methodas in claim 3, wherein a third of the one or more priority rulescomprises prioritizing a transmission associated with a primary mediumaccess control (MAC) instance over a transmission associated with asecondary MAC instance, wherein the primary MAC instance is associatedwith one of the first and second data paths, and wherein the secondaryMAC instance is associated with the other one of the first and seconddata paths.
 6. The method as in claim 1, wherein the first transmissionis transmitted to a first serving site and the second transmission istransmitted to a second serving site.
 7. The method as in claim 6,wherein the first transmission is scheduled via a first uplink grantreceived from the first serving site and the second transmission isscheduled via a second uplink grant received from the second servingsite.
 8. The method as in claim 1, further comprising: receivingsignaling to configure the first independent maximum transmit power andthe second independent maximum transmit power, and configuring the WTRUwith the first independent maximum transmit power and the secondindependent maximum transmit power.
 9. The method as in claim 1, whereinthe first and second independent maximum transmit powers are specific tofirst and second bandwidth parts, respectively.
 10. The method as inclaim 1, wherein the one or more priority rules comprises a rule toscale the second transmission power if the sum of the first and secondtransmission powers exceeds a total maximum transmit power.
 11. Awireless transmit/receive unit (WTRU) comprising: a processor configuredto: utilize a first physical layer configuration for transmissionsassociated with a first data path associated with a first group ofcells, wherein the first group of cells comprises a primary cell andzero or more secondary cells and utilizes a first radio accesstechnology, and wherein the first physical layer configuration isconfigured for frequency division duplexing (FDD) of the transmissionsexchanged with at least the primary cell of the first group of cells,utilize a second physical layer configuration for transmissionsassociated with a second data path associated with a second group ofcells, wherein the second group of cells comprises a primary cell andzero or more secondary cells and utilizes a second radio accesstechnology, and wherein the second physical layer configuration isconfigured for time division duplexing (TDD) of the transmissionsexchanged with at least one of the primary cell and the zero or moresecondary cells, and allocate a first transmission power for a firsttransmission to be sent to the primary cell of the first group of cellsvia the first data path and a second transmission power for a secondtransmission to be sent to the at least one of the primary cell and thezero or more secondary cells via the second data path, wherein: thefirst and second transmissions at least partially overlap in time; andat least a portion of one or more of the first transmission power andthe second transmission power is allocated based on (i) whether thefirst and second transmissions are to be sent on carriers within thesame frequency range or on carriers within different frequency ranges,(ii) first and second independent maximum transmit powers forconstraining the first and second transmission powers, respectively, and(iii) one or more priority rules related to the first transmission beingsent via the first data path and the second transmission being sent viathe second data path; and a transmitter configured to transmit the firstand second transmissions using respective Uu interfaces.
 12. The WTRU asin claim 11, wherein a first of the one or more priority rules comprisesprioritizing a transmission that includes uplink control information(UCI) over a transmission that does not include UCI.
 13. The WTRU as inclaim 12, wherein a second of the one or more priority rules comprisesprioritizing a transmission that includes a first type of UCI over atransmission that includes a second type of UCI.
 14. The WTRU as inclaim 13, wherein the first type of UCI comprises hybrid automaticrepeat request (HARQ) feedback and the second type of UCI compriseschannel quality information (CQI).
 15. The WTRU as in claim 13, whereina third of the one or more priority rules comprises prioritizing atransmission associated with a primary medium access control (MAC)instance over a transmission associated with a secondary MAC instance,wherein the primary MAC instance is associated with one of the first andsecond data paths, and wherein the secondary MAC instance is associatedwith the other one of the first and second data paths.
 16. The WTRU asin claim 11, wherein the first transmission is transmitted to a firstserving site and the second transmission is transmitted to a secondserving site.
 17. The WTRU as in claim 16, wherein the firsttransmission is scheduled via a first uplink grant received from thefirst serving site and the second transmission is scheduled via a seconduplink grant received from the second serving site.
 18. The WTRU as inclaim 11, wherein the WTRU comprises a receiver and wherein the receiveris configured to receive signaling to configure the first independentmaximum transmit power and the second independent maximum transmitpower, and wherein the processor is configured to configure the WTRUwith the first independent maximum transmit power and the secondindependent maximum transmit power.
 19. The WTRU as in claim 11, whereinthe first and second independent maximum transmit powers are specific tofirst and second bandwidth parts, respectively.
 20. The WTRU as in claim11, wherein the one or more priority rules comprises a rule to scale thesecond transmission power if the sum of the first and secondtransmission powers exceeds a total maximum transmit power.